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Robotic Spacecraft (Astronomy, Planetary, Earth, Solar/Heliophysics) => Space Science Coverage => Topic started by: Star One on 11/25/2016 11:40 PM

Title: Boyajians Star Updates And Discussion
Post by: Star One on 11/25/2016 11:40 PM
Is currently being observed by the Allen Telescope Array.

http://setiquest.info

Only reached a pretty common on 2.
Title: Re: Boyajians Star Updates And Discussion
Post by: Req on 11/26/2016 06:46 PM
I suppose if we're going to be arbitrary about naming this star, I hereby declare it Req's star!  Thread #3(or is it 4) incoming!

Edit so that this post isn't pure snark, for searches:

KIC 8462852
KIC8462852
Tabby's Star
Tabbys Star
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 11/26/2016 07:00 PM
The main problem with the previous thread is that it seems to be undergoing an extreme dimming event so that it's not even observable any more.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 11/26/2016 07:27 PM
I suppose if we're going to be arbitrary about naming this star, I hereby declare it Req's star!  Thread #3(or is it 4) incoming!

This name has been applied to be its official name I believe.
Title: Re: Boyajians Star Updates And Discussion
Post by: Johnnyhinbos on 11/26/2016 10:21 PM
The main problem with the previous thread is that it seems to be undergoing an extreme dimming event so that it's not even observable any more.
Lol - I see what you did there...
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 11/28/2016 07:13 PM
Not strictly related but can anyone explain the significance of this new Tweet by Jason Wright?

Quote
Jason Wright –  ‏@Astro_Wright

@EricMamajek Now that we have a TGAS distance & space motion, is it weird that TYC 8830-410-1 has a big IR excess?
http://adsabs.harvard.edu/abs/2016ApJS..225...15C …

This is the only reference I can find and it's a little old.

http://adsabs.harvard.edu/abs/2015sofi.prop..130S
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 11/28/2016 10:47 PM
Well this is just a guess but; often when you are talking about a star's position and motion through the galaxy you are using it as a proxy for age.  I would assume what he's alluding to is the space motion implies it comes from an old population, one which shouldn't be undergoing a LHB to keep the dust hot.
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 11/28/2016 10:50 PM
Not strictly related but can anyone explain the significance of this new Tweet by Jason Wright?

Quote
Jason Wright –  ‏@Astro_Wright

@EricMamajek Now that we have a TGAS distance & space motion, is it weird that TYC 8830-410-1 has a big IR excess?
http://adsabs.harvard.edu/abs/2016ApJS..225...15C …

This is the only reference I can find and it's a little old.

http://adsabs.harvard.edu/abs/2015sofi.prop..130S

Eric Mamajek is an expert on circumstellar disks and planetary formation.  I don't know if he has commented on Tabby's star anywhere.  The tweet looks like it was an "inside" message from Wright, who is looking for mechanisms to explain the lack of IR excess around Tabby's star, to an expert who has contributed to the knowledge base of transient warm disks around stars like TYC 8830-410-1.

Is Wright looking for confirmation or issuing a challenge?   I don't know.  Lately he seems to favor the ISM as the reason for dimming of Tabby's star, but that still leaves the problem of IR excess.   Maybe Wright is postulating that depending on the clumpiness of the ISM, and the proper motion of Tabby's star relative the the motion if the ISM, you could get IR excess only when a big dimming event is happening.   Then it is gone after the event, and any dust farther out of the system is cold, and would not produce the IR flux missing at Tabby's star?  Eric Mamajek is the type of expert that may have something to say about that.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 11/28/2016 10:52 PM
Well this is just a guess but; often when you are talking about a star's position and motion through the galaxy you are using it as a proxy for age.  I would assume what he's alluding to is the space motion implies it comes from an old population, one which shouldn't be undergoing an LHB to keep the dust hot.

People keep wanting alien megastructures well if it was one of them it could be giving off a huge excess of IR. It does throw you into that territory if you get something like this around an older star.

I did wonder if he was alluding to its age so thanks for the thoughts on that.

He's has had a reply now.

Quote
Eric Mamajek –  ‏@EricMamajek

@Astro_Wright @steinly0 I'll be visiting your dept Wed am - can chat then on this object
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 11/28/2016 11:01 PM
By the way there's a new paper on the star that is the topic of this thread.

A physically inspired model of Dip d792 and d1519 of the Kepler light curve seen at KIC8462852

Quote
The star KIC 8462852 shows a very unusual and hard to comprehend light curve. The dip d7922 absorbs 16% of the starlight. The light curve is unusually smooth but the very steep edges make it hard to find a simple natural explanation by covering due to comets or other well-known planetary objects. We describe a mathematical approximation to the light curve, which is motivated by a physically meaningful event of a large stellar beam which generates an orbiting cloud. The data might fit to the science fiction idea of star lifting, a mining technology that could extract star matter. We extend the model to d1519 and d1568 using multiple beams and get an encouraging result that fits essential parts of the dips but misses other parts of the measured flux. We recommend further exploration of this concept with refined models.

https://arxiv.org/abs/1611.08368

I believe this is going up for peer review as well.

There is also this Where's The Flux update.

http://www.wherestheflux.com/single-post/2016/11/28/October-science-update-Part-II

One thing to note is it's going to be observed by Swift.
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 11/29/2016 01:19 AM
From the paper by Eduard Heindl at:
https://arxiv.org/abs/1611.08368
Quote
3. The Model

The main aim of this paper is a physical model for the flux variation of the dip at day 792.
The model is based on the idea, that a stream of matter leaves the star into space similar as
observed in solar flares. The difference is, the stream of matter is quite high and lifts the
matter into a stable orbit. It is not the aim of this paper to speculate for the mechanic of this
event in detail.

Bold & underline is my addition.

The beam model was briefly discussed in the "WTF" thread.  The fit of the model to the data is interesting.   The paper would have done itself a favor if it ended after section 5.    The last 2 pages does exactly what it said was not the aim, which was to bring in the ETI hypothesis as the explanation for the mechanics of the dimming.

It would be interesting to see how the paper gets reviewed if all reference to star lifting was scrubbed.  It have the feeling it would be like the EM Drive threads where current work on EM drives show some resultant force without any basis in physics as is currently understood to offer an explanation of how it works.

I think the paper may also suffer from some language barriers.  The proposal of a lifted beam ( or CME) with a trail of "smoke" makes no sense.   What becomes of a CME when it condenses, or is no longer ejected plasma?
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 11/29/2016 05:54 AM
From the paper by Eduard Heindl at:
https://arxiv.org/abs/1611.08368
Quote
3. The Model

The main aim of this paper is a physical model for the flux variation of the dip at day 792.
The model is based on the idea, that a stream of matter leaves the star into space similar as
observed in solar flares. The difference is, the stream of matter is quite high and lifts the
matter into a stable orbit. It is not the aim of this paper to speculate for the mechanic of this
event in detail.

Bold & underline is my addition.

The beam model was briefly discussed in the "WTF" thread.  The fit of the model to the data is interesting.   The paper would have done itself a favor if it ended after section 5.    The last 2 pages does exactly what it said was not the aim, which was to bring in the ETI hypothesis as the explanation for the mechanics of the dimming.

It would be interesting to see how the paper gets reviewed if all reference to star lifting was scrubbed.  It have the feeling it would be like the EM Drive threads where current work on EM drives show some resultant force without any basis in physics as is currently understood to offer an explanation of how it works.

I think the paper may also suffer from some language barriers.  The proposal of a lifted beam ( or CME) with a trail of "smoke" makes no sense.   What becomes of a CME when it condenses, or is no longer ejected plasma?

Why would the author delete such sections when it's clear that's one of the topics he wants to discuss.

Just because you may happen to not to agree with this hypothesis does not mean that such a debate should be stifled.
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 11/29/2016 06:34 AM

Why would the author delete such sections when it's clear that's one of the topics he wants to discuss.

Just because you may happen to not to agree with this hypothesis does not mean that such a debate should be stifled.

The author, Mr. Heindl, said that "It is not the aim of this paper to speculate for the mechanic of this
event in detail",...
and he then went about doing just that by including all the speculation on starlifting by ETI's. 

I'm OK with speculation on starlifting,  I don't want to stifle anything,  however his paper forfeits congruity by saying one thing and then doing another.  I think the paper may be more interesting if he would have focused on demonstrating the strong fit of modeling a "beam" of matter extended from the stars surface as the mechanism of the dimming, and leave out all ETI speculation.  The paper will likely be dismissed by serious academics for including these claims that would better off bifurcated & discussed separate from the ETI hypothesis.

It is logically more palatable to just make supportable proposals as to what the source of the dimming might be, when the more controversial argument is the cause. (i.e ETI's) 

The same goes for J. Wrights proposal for ISM/bok globules.   The body of knowledge regarding the internal structure of bok globules or other ISM is pretty sparse.   However each proposal has to first demonstrate it can "model" the dimming, and then subsequent predictions for future observations can test the hypothesis.



Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 11/29/2016 06:46 AM

Why would the author delete such sections when it's clear that's one of the topics he wants to discuss.

Just because you may happen to not to agree with this hypothesis does not mean that such a debate should be stifled.

The author, Mr. Heindl, said that "It is not the aim of this paper to speculate for the mechanic of this
event in detail",...
and he then went about doing just that by including all the speculation on starlifting by ETI's. 

I'm OK with speculation on starlifting,  I don't want to stifle anything,  however his paper forfeits congruity by saying one thing and then doing another.  I think the paper may be more interesting if he would have focused on demonstrating the strong fit of modeling a "beam" of matter extended from the stars surface as the mechanism of the dimming, and leave out all ETI speculation.  The paper will likely be dismissed by serious academics for including these claims that would better off bifurcated & discussed separate from the ETI hypothesis.

It is logically more palatable to just make supportable proposals as to what the source of the dimming might be, when the more controversial argument is the cause. (i.e ETI's) 

The same goes for J. Wrights proposal for ISM/bok globules.   The body of knowledge regarding the internal structure of bok globules or other ISM is pretty sparse.   However each proposal has to first demonstrate it can "model" the dimming, and then subsequent predictions for future observations can test the hypothesis.

Again you have not answered the point why shouldn't they at least discuss these matters other to confirm to some kind of institutional bias.
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 11/29/2016 02:31 PM

Again you have not answered the point why shouldn't they at least discuss these matters other to confirm to some kind of institutional bias.
I gave 4 reasons why the paper would have been better off by omitting ETI speculation. 

If one submits a paper on the arvix server and invites review and criticism, it might be a better approach to stick to your best argument.   Confronting the institutional bias against ETI's is not likely helpful in getting the main argument heard & reviewed with any respect.

Title: Re: Boyajians Star Updates And Discussion
Post by: TakeOff on 11/29/2016 07:46 PM
There used to be a long thread here about the WTF star. But that seems to suddenly have dipped down by 100% without any kind of explanation. Maybe there's a filter here?

In that thread I were convinced that this kind of dimmings where astrophysical and had nothing to do with human actions or software bugs on Earth. But this sudden total disappearance of one specific thread here kind of confounds me. Was it maybe a binary neutron star merger that caused it? Is there any secondary observation to confirm it?
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 11/29/2016 07:55 PM
I believe human actions or software bugs on Earth are good candidates for this second kind of dimming. But in common with the stellar brightness fluctuations, the phenomenon seems to be impossible to predict in advance.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 12/03/2016 09:52 PM
Same old, same old.

A not unexpected null result.

Quote
RADIO SETI OBSERVATIONS OF THE ANOMALOUS STAR KIC 8462852
G. R. Harp1, Jon Richards1, Seth Shostak1, J. C. Tarter1, Douglas A. Vakoch1,2, and Chris Munson1
Published 2016 July 13 • 2016. The American Astronomical Society. All rights reserved.
The Astrophysical Journal, Volume 825, Number 2

http://iopscience.iop.org/article/10.3847/0004-637X/825/2/155
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 12/04/2016 09:19 PM
I understand it is necessary to put limits on the speculation regarding advanced civlizations around Tabby's star, but I do kind of lament the uselessness of the effort, as well as how it will likely be misused by skeptics to say that the Allen array looked for a signal and didn't detect anything, therefore the ETI hypothesis is disproven.

From the article:

Quote
These limits correspond to isotropic radio transmitter powers of (4–7) 1015 W and 1019 W for the narrowband and moderate band observations. These can be compared with Earth's strongest transmitters, including the Arecibo Observatory's planetary radar (2 1013 W EIRP). Clearly, the energy demands for a detectable signal from KIC 8462852 are far higher than this terrestrial example (largely as a consequence of the distance of this star). On the other hand, these energy requirements could be very substantially reduced if the emissions were beamed in our direction.

So the observation rules out transmissions that greater than a petawatt or exawatt scale isotropic source.   There is no way to make any assessment of the ETI hypothesis from the observation, as a nullification or in support.  It just "is what it is".   

I just hope the next dimming event is caught by multiple ground and space based observatories.   
Title: Re: Boyajians Star Updates And Discussion
Post by: Johnnyhinbos on 12/04/2016 09:24 PM
We're talking about events that happened 1,400 years ago, is this correct?
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 12/04/2016 10:10 PM
We're talking about events that happened 1,400 years ago, is this correct?

That is correct.
Title: Re: Boyajians Star Updates And Discussion
Post by: Johnnyhinbos on 12/05/2016 01:30 AM
So if there was a Dyson sphere being constructed some 1,400 years ago, wouldn't there be some much greater probability of seeing such a thing in our neighborhood some 1,400 years later?

(Queue the Fermi paradox comment...)

Title: Re: Boyajians Star Updates And Discussion
Post by: rocx on 12/05/2016 07:03 AM
So if there was a Dyson sphere being constructed some 1,400 years ago, wouldn't there be some much greater probability of seeing such a thing in our neighborhood some 1,400 years later?

(Queue the Fermi paradox comment...)

No, because travel to our neighbourhood would necessarily take longer than 1400 years.
Title: Re: Boyajians Star Updates And Discussion
Post by: LouScheffer on 12/05/2016 02:53 PM
[...] I do kind of lament the uselessness of the effort [...]

From the article:
Quote
These limits correspond to isotropic radio transmitter powers of (4–7) 1015 W and 1019 W for the narrowband and moderate band observations. These can be compared with Earth's strongest transmitters, including the Arecibo Observatory's planetary radar (2 1013 W EIRP). Clearly, the energy demands for a detectable signal from KIC 8462852 are far higher than this terrestrial example (largely as a consequence of the distance of this star). On the other hand, these energy requirements could be very substantially reduced if the emissions were beamed in our direction.
So the observation rules out transmissions that greater than a petawatt or exawatt scale isotropic source.   There is no way to make any assessment of the ETI hypothesis from the observation, as a nullification or in support.  It just "is what it is".   
The key here is the very substantially reduced in the abstract.  If they know we are here, and might be listening, then the power requirements can be quite modest.  In fact. 1 watt (not a typo) would suffice.  They need to cover a disc of about 1 AU centered around our star.  That's a radius of 1.5e11 meters, or an area of about 7e22 m^2.  1 watt produces 1.3e-23 w/m^2, an intensity we can detect narrowband.  (To see this is indeed plausible, note that we can detect the carriers from spacecraft at Mars even when the are using their omni-directional antennas and just a few watts.  That's a similar intensity).

Now this would require a very big (by Earth standards) transmitting antenna (to make a 10^11 m spot from 10^19 meters away takes an antenna about 10^8 wavelengths across, or 3000 km at a 3 cm wavelength).   But there are other compromises, such as 10 kw from a 30 km size antenna, or 1 MW from a 3 km antenna (that's just a factor 6 bigger than Earth technology).  And if the antenna was a phased array, not a dish, they could send signals to all potential recipients in a half sphere simultaneously, so they do not have to be targetting just us.

Anyone who might send us a signal probably already knows there is a life-bearing planet in our system, since we are (on a historical scale) close to this technology already.  So assuming they wanted to send a signal, they could target just those, for a modest investment in power and technology.   So it's not useless to look.
 


Title: Re: Boyajians Star Updates And Discussion
Post by: notsorandom on 12/05/2016 03:28 PM
Sending a signal over a thousand light years means figuring out where the target will be over a thousand years from now. Even a small fraction of a meter per second unaccounted for in the prediction of the star's motion over a thousand year can throw the beam wildly off target.
Title: Re: Boyajians Star Updates And Discussion
Post by: LouScheffer on 12/05/2016 04:10 PM
Sending a signal over a thousand light years means figuring out where the target will be over a thousand years from now. Even a small fraction of a meter per second unaccounted for in the prediction of the star's motion over a thousand year can throw the beam wildly off target.
As above, they need an angular accuracy of about 1 part in 10^8, projected 1400 years out (actually about twice that, since the observer sees where they were 1400 years ago, and needs to predict where they will be 1400 years from now).  Gaia, in orbit now, is measuring positions to about 1 part in 10^10.  So if the mission lasts 30 years (or better yet, 2 Gaia-like missions 100 or more  years apart), your aiming data should be more than good enough.  So aiming is likely not the limiting factor.
Title: Re: Boyajians Star Updates And Discussion
Post by: JasonAW3 on 12/05/2016 04:57 PM

      I hate to bring this up, but if one is expecting possible communications from a nonterrestrial source, such as Tabby's Star, has anyone considered the possibility of modulated X-rays?

      NASA is currently studying this as a potential alternative to both RF and lasers.  Apparently, not only is there far less signal diffusion from an X-ray laser, rather than an optical laser, but due to the wavelength, far more data can be encoded into such a beam, and transmitted with far less signal loss from both distance and potential obscuring gas clouds.

      There's always been the speculation that if there is sapient life, other than ourselves, in space, that they might use something other than radio waves to communicate over vast distances.
Title: Re: Boyajians Star Updates And Discussion
Post by: notsorandom on 12/05/2016 06:47 PM
Sending a signal over a thousand light years means figuring out where the target will be over a thousand years from now. Even a small fraction of a meter per second unaccounted for in the prediction of the star's motion over a thousand year can throw the beam wildly off target.
As above, they need an angular accuracy of about 1 part in 10^8, projected 1400 years out (actually about twice that, since the observer sees where they were 1400 years ago, and needs to predict where they will be 1400 years from now).  Gaia, in orbit now, is measuring positions to about 1 part in 10^10.  So if the mission lasts 30 years (or better yet, 2 Gaia-like missions 100 or more  years apart), your aiming data should be more than good enough.  So aiming is likely not the limiting factor.
How predictable are stellar motions throughout the galaxy over that timeframe? Over a long enough timeline small but unaccounted for perturbations make all orbits somewhat unpredictable.
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 12/05/2016 07:23 PM
How predictable are stellar motions throughout the galaxy over that timeframe? Over a long enough timeline small but unaccounted for perturbations make all orbits somewhat unpredictable.

Even a few thousand years is a very short time when you are considering motion of stars in the Milky Way. I haven't done any calculations to back it up, but it seems to me that if you had the technology to build a sender with good enough directionality to make the proper motion of stars worth considering, you would also have the technology to measure the proper motion to high enough precision.
Title: Re: Boyajians Star Updates And Discussion
Post by: Vultur on 12/10/2016 01:58 AM
A hypothetical civilization capable of building structures large enough to cause the Boyajian's star dimming events certainly could beam signals to us.

But we're really not that close, and there seem to be a lot of planets in the galaxy.

Any signal that we could receive now would have been sent 1400 years ago... and their information on Earth would be how it looked 2800 years ago, in the time of Homer in Greece and the Zhou Dynasty in China. So no radio signals from Earth, no evidence of industrial pollution in spectroscopy of Earth's atmosphere, no night side lights (even if they had super-interferometry telescopes good enough to see those).

So why would they pick Earth to send signals to? What would make them think there'd be a civilization here able to receive it?
Title: Re: Boyajians Star Updates And Discussion
Post by: Johnnyhinbos on 12/10/2016 07:13 AM
To get to the point of my earlier comment - that we are looking at a star 1,400 years in the past - and it is a bit nuanced, but in a nutshell - if a civilization had survived to the point of maturity to be able to build a Dyson sphere (aka a Type II civilization on the Kardashev scale) some 1,400 years ago, then in our existence, 1,400 years later, the galaxy should be filled with intelligent radiation. Since it's not then it's doubtful that said civilization ever got to such a point in the first place.

Numerically speaking, think of the Carter catastrophe, and apply it to the Fermi paradox.

Therefore, sadly, I highly doubt the dimming events are caused by another civilization.
Title: Re: Boyajians Star Updates And Discussion
Post by: JH on 12/10/2016 07:53 AM
Your conclusion suffers from the same problem as all applications of the German tank problem to civilizational survival: rigid application of statistics with incomplete knowledge of constraints. How do you know that the aliens in question aren't just homebodies?

To be clear, I think a natural explanation for the dimmings of Boyajian's star is much more likely than aliens.

- typo
Title: Re: Boyajians Star Updates And Discussion
Post by: LouScheffer on 12/10/2016 06:36 PM
A hypothetical civilization capable of building structures large enough to cause the Boyajian's star dimming events certainly could beam signals to us.

But we're really not that close, and there seem to be a lot of planets in the galaxy.

Any signal that we could receive now would have been sent 1400 years ago... and their information on Earth would be how it looked 2800 years ago, in the time of Homer in Greece and the Zhou Dynasty in China. So no radio signals from Earth, no evidence of industrial pollution in spectroscopy of Earth's atmosphere, no night side lights (even if they had super-interferometry telescopes good enough to see those).

So why would they pick Earth to send signals to? What would make them think there'd be a civilization here able to receive it?
In this situation, one possibility is that Earth gets no special treatment - they send signals in the direction of all life-bearing planets they know about.  If they can build Dyson spheres, they probably know the Earth exists, and has at least a good chance of having life.  They would know, for example, that oxygen and methane co-exist in our atmosphere.  Since these react on a short time scale, that means there is an active source of each.  I don't think we know of any non-life explanation for this.

The technology to send signals to multiple planets simultaneously is straightforward using phased array antennas.  Using existing Earth technology, we could send signals that we ourselves could detect to all the planets we have discovered so far, if we wanted to (See Appendix B of the book "SETI 2020" for several ways this might be done.)   Aliens presumably know of more planets, but can build larger sending arrays to compensate.  The power requirements are modest since the beams are highly directional.

The main advantage of this strategy is that communication does not depend on long lifetimes for technical civilizations.  If they wait until they see we have technology, then even if they reply right away, then we won't know of them for at least 2800 years after technology development.  If they signal in advance, we could find it after only a few decades of technology, and might even reply.  Depending on what we chose to send, they could find out quite a bit about us even if the lifetime of our civilization is short.


Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 12/10/2016 07:14 PM
A hypothetical civilization capable of building structures large enough to cause the Boyajian's star dimming events certainly could beam signals to us.

But we're really not that close, and there seem to be a lot of planets in the galaxy.

Any signal that we could receive now would have been sent 1400 years ago... and their information on Earth would be how it looked 2800 years ago, in the time of Homer in Greece and the Zhou Dynasty in China. So no radio signals from Earth, no evidence of industrial pollution in spectroscopy of Earth's atmosphere, no night side lights (even if they had super-interferometry telescopes good enough to see those).

So why would they pick Earth to send signals to? What would make them think there'd be a civilization here able to receive it?
In this situation, one possibility is that Earth gets no special treatment - they send signals in the direction of all life-bearing planets they know about.  If they can build Dyson spheres, they probably know the Earth exists, and has at least a good chance of having life.  They would know, for example, that oxygen and methane co-exist in our atmosphere.  Since these react on a short time scale, that means there is an active source of each.  I don't think we know of any non-life explanation for this.

The technology to send signals to multiple planets simultaneously is straightforward using phased array antennas.  Using existing Earth technology, we could send signals that we ourselves could detect to all the planets we have discovered so far, if we wanted to (See Appendix B of the book "SETI 2020" for several ways this might be done.)   Aliens presumably know of more planets, but can build larger sending arrays to compensate.  The power requirements are modest since the beams are highly directional.

The main advantage of this strategy is that communication does not depend on long lifetimes for technical civilizations.  If they wait until they see we have technology, then even if they reply right away, then we won't know of them for at least 2800 years after technology development.  If they signal in advance, we could find it after only a few decades of technology, and might even reply.  Depending on what we chose to send, they could find out quite a bit about us even if the lifetime of our civilization is short.

This of course leaves out the "why" question. As in why they would want to send all these signals out. Maybe they're as smart as Stephen Hawking, and realise that it is kind of a dangerous thing to do. Rather finish your "Death Star' device as much as possible before announcing your existence to the Universe.
Title: Re: Boyajians Star Updates And Discussion
Post by: LouScheffer on 12/10/2016 07:58 PM

This of course leaves out the "why" question.
They *why* part is really hard.  Imagine asking someone who lived 2800 years ago why we do all the various stuff we do today.  And that's the same civilization, on the same planet, with the same biology.  Add in different planet, different civilization, different biology, and potentially millions of years of development, and every conclusion needs to be treated as a guess.
Quote
Maybe they're as smart as Stephen Hawking, and realise that it is kind of a dangerous thing to do. Rather finish your "Death Star' device as much as possible before announcing your existence to the Universe.
Alternatively, it's perhaps more likely that anyone who is capable of coming here and beating us up, already knows (or will know, subject to the speed of light) about us whether we signal or not.  In that case it's better to make friends, see if they have any suggestions, and spread what we know.

Any conclusion that depends on the motivation of aliens is in very murky territory.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 12/10/2016 10:20 PM
I was reading a little while back that there may have been indications of planets orbiting this star but nothing terribly definitive as they probably aren't transiting from our prospective. There apparently was an indication of a brown dwarf.
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 12/11/2016 06:15 AM
I was reading a little while back that there may have been indications of planets orbiting this star but nothing terribly definitive as they probably aren't transiting from our prospective. There apparently was an indication of a brown dwarf.
Source? I haven't seen anything like that, and it should be big news if there is any serious evidence. Not clear what kind of evidence that could be based on either, I guess a BD or giant planet could be picked up in radial velocity.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 12/11/2016 08:25 AM
I was reading a little while back that there may have been indications of planets orbiting this star but nothing terribly definitive as they probably aren't transiting from our prospective. There apparently was an indication of a brown dwarf.
Source? I haven't seen anything like that, and it should be big news if there is any serious evidence. Not clear what kind of evidence that could be based on either, I guess a BD or giant planet could be picked up in radial velocity.

Mods on the relevant Reddit who I believe some of which are professional astronomers.

https://m.reddit.com/r/KIC8462852/comments/5he29u/orbiting_planets_around_kic8462852/
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 12/11/2016 08:43 AM
Mods on the relevant Reddit who I believe some of which are professional astronomers.

https://m.reddit.com/r/KIC8462852/comments/5he29u/orbiting_planets_around_kic8462852/
Thanks. I suspect that that
Quote
There probably are planets, but they aren't transiting (no surprise), and they are too small or too inclined to make a dent in the radial velocity measurements we have to date
is just meant in the general sense that most stars have planets, so this one probably does too.

Quote
There is a dwarf possibly in the system.
presumably refers to the previously identified M dwarf, which may or may not be associated.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 12/11/2016 02:24 PM
Mods on the relevant Reddit who I believe some of which are professional astronomers.

https://m.reddit.com/r/KIC8462852/comments/5he29u/orbiting_planets_around_kic8462852/
Thanks. I suspect that that
Quote
There probably are planets, but they aren't transiting (no surprise), and they are too small or too inclined to make a dent in the radial velocity measurements we have to date
is just meant in the general sense that most stars have planets, so this one probably does too.

Quote
There is a dwarf possibly in the system.
presumably refers to the previously identified M dwarf, which may or may not be associated.

Will Gaia observations be able to confirm if it is associated or not?
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 12/11/2016 02:49 PM
I think the (possible) companion star is a bit too faint for Gaia.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 12/12/2016 07:39 PM
From Jason Wright's Twitter.

https://mobile.twitter.com/Astro_Wright/status/808343603902746624/photo/1
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 12/13/2016 10:37 AM
I think the (possible) companion star is a bit too faint for Gaia.

Very likely, which is a shame: we'd be much more likely to be able to see the orbital motion on the M companion than on the A3V primary (if they're bound) ...

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 12/13/2016 10:58 AM
I think the (possible) companion star is a bit too faint for Gaia.

Very likely, which is a shame: we'd be much more likely to be able to see the orbital motion on the M companion than on the A3V primary (if they're bound) ...

--- Tony

A3V?
Title: Re: Boyajians Star Updates And Discussion
Post by: jgoldader on 12/13/2016 12:14 PM
I think the (possible) companion star is a bit too faint for Gaia.

Very likely, which is a shame: we'd be much more likely to be able to see the orbital motion on the M companion than on the A3V primary (if they're bound) ...

--- Tony

A3V?

Spectral type A3, luminosity class 5 (main sequence dwarf).  The Sun is G2V.  The spectral type sequence reflects temperature, and goes (from hottest to coldest) OBAFGKM (I am not including the brown dwarfs).  Each spectral type goes from subtype 0 to 9 (e.g., G0 is warmer than G1, etc., then G9, then K0).  Luminosity classes go from I to V, in order of decreasing luminosity.  It depends on the temperature and radius of the star.  Supergiants are the class I, dwarfs (normal core hydrogen burning stars) are V.

How we ended up with those letters (OBAFGKM) is a fascinating story, but way beyond the scope of this post!
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 12/13/2016 12:49 PM

Spectral type A3, luminosity class 5 (main sequence dwarf).  The Sun is G2V.  The spectral type sequence reflects temperature, and goes (from hottest to coldest) OBAFGKM (I am not including the brown dwarfs).  Each spectral type goes from subtype 0 to 9 (e.g., G0 is warmer than G1, etc., then G9, then K0).  Luminosity classes go from I to V, in order of decreasing luminosity.  It depends on the temperature and radius of the star.  Supergiants are the class I, dwarfs (normal core hydrogen burning stars) are V.

How we ended up with those letters (OBAFGKM) is a fascinating story, but way beyond the scope of this post!

I meant that I didn't think the primary is an A star and now that I've checked, it seems to be F3V.

Not that there's anything wrong with your explanation ;)
Title: Re: Boyajians Star Updates And Discussion
Post by: jgoldader on 12/13/2016 01:49 PM


I meant that I didn't think the primary is an A star and now that I've checked, it seems to be F3V.


Yer right, I didn't catch that.  D'oh.

Nothing to see here everyone, carry on, carry on.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 12/19/2016 08:07 PM
Short documentary about this subject.

https://m.youtube.com/watch?v=Mh5C6b_GYyM
Title: Re: Boyajians Star Updates And Discussion
Post by: Mongo62 on 12/20/2016 01:03 AM
Mysterious eclipses in the light-curve of KIC8462852: a possible explanation (https://arxiv.org/abs/1612.06121)

ABSTRACT:

Apart from thousands of 'regular' exoplanet candidates, Kepler satellite has discovered a few stars exhibiting peculiar eclipse-like events. They are most probably caused by disintegrating bodies transiting in front of the star. However, the nature of the bodies and obscuration events, such as those observed in KIC8462852, remain mysterious. Swarm of comets or artificial alien mega-structures have been proposed as an explanation for the latter object.

We explore the possibility that such eclipses are caused by the dust clouds associated with massive parent bodies orbiting the host star.

We assume a massive object and a simple model of the dust cloud surrounding the object. Then, we use the numerical integration to simulate the evolution of the cloud, its parent body, and resulting light-curves as they orbit and transit the star.

It is found that it is possible to reproduce the basic features in the light-curve of KIC8462852 with only four objects enshrouded in dust clouds. The fact that they are all on similar orbits and that such models require only a handful of free parameters provide additional support for this hypothesis.

This model provides an alternative to the comet scenario. With such physical models at hand, at present, there is no need to invoke alien mega-structures into the explanation of these light-curves.

7. Conclusions

Our main findings and arguments are briefly summarized below.

1. It was demonstrated that it is possible to explain the complex morphology of the Kepler light-curve of KIC8462852 with a very simple model. Only four massive objects, each surrounded by a dust cloud can account for most of the observed features. The objects are apparently of a common origin i.e. a result of a break-up process of a single progenitor.

2. Most of the features may be represented by a simple, initially spherical dust cloud. Such clouds in eccentric orbits are observed to naturally vertically shrink and develop a leading tail as they approach periastron. The feature at 1 540 days seems to be special since it is best reproduced by an initially ring-like structure.

3. This scenario of 4 massive objects is further supported by the following arguments: the smooth shape of the 800 day feature which is difficult to assemble from a number of smaller objects such as comets; a tendency towards shallower ingress and steeper egress of the 800 day feature which is just the opposite of what is expected for the less massive objects such as comets; the 1 520 and 1 570-day features also show a gradual increase in strengths of individual ’sub-features’ and fast recovery what resembles the 800 day feature; the symmetric ’ring-like’ structure of the 1 540-day feature which would presume a non-negligible gravity of the object; the very existence of another symmetric structure at 1 210 days which is very similar to the above mentioned feature and which is difficult to understand within comet scenario or other models; the clustering of the obscuration features into 4 main events which naturally leads to the association with four objects; as well as by the fact that our solution indicates that all four bodies are on very similar eccentric orbits. Apart from that all best fits were for the P-R drag parameter β = 0.629 what indicates that also the dust particles may be similar in size and chemical composition.

4. It is not claimed that we found the only/best solution within this concept of 4 massive bodies. We rather state that we found a possible solution.

5. Iron or carbon grains smaller than about 0.1 micron experience a very strong radiative push which quickly disconnects them from the parent body and places them on hyperbolic orbits. Thus it is unlikely that such grains contribute significantly to the observed features.

6. Grains larger than about 100 microns experience small radiative accelerations and may remain bound to the massive object. Their opacity is small so they are not likely to contribute significantly to the obscuration events. However, they may act as a reservoir and produce smaller dust grains via collisions.

7. It is argued that 0.3−10 micron size dust grains are the best candidates to explain the obscuration events. Smaller grains, unless they were being replenished, would be easily expelled from the system while larger grains would have a relatively small opacity.

8. It was shown that the mutual interaction between the massive objects and their dust clouds within few astronomical units from the periastron can be neglected and that they can be treated independently of each other in this region.

9. If the two massive objects follow each other on identical eccentric orbits with a short enough time lag, a strong interaction between them and their dust clouds may happen at larger distances from the star which might disperse the clouds but, at the same time, also expose sub-surface volatile material, trigger outbursts and produce debris.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 12/20/2016 07:37 PM
Viewpoint: New Clues as to Why Boyajian’s Star is Dimming

A statistical analysis links a star’s mysterious brightness fluctuations to internal nonequilibrium phenomena, rather than structures orbiting around the star.

http://physics.aps.org/articles/v9/150
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 12/21/2016 08:48 PM
Thoughts on Neslušan and Buda

By Jason Wright

http://sites.psu.edu/astrowright/2016/12/21/thoughts-on-neslusan-and-budaj/
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 12/22/2016 07:12 PM
Quote
Jason Wright ‏@Astro_Wright
Inaugural K-band #BreakthroughListen observations underway at 22 GHz at @GrnBnkTelescope. Target:@tsboyajian's Star. #SETI
Moist Chure
3h
Moist Chure ‏@MoistChure
@Astro_Wright @GrnBnkTelescope @tsboyajian How long till SETI analyzes the data?
Jason Wright
3h
Jason Wright ‏@Astro_Wright
@MoistChure @GrnBnkTelescope @tsboyajian First we have to get it to PSU, then I have to learn the software. Timescale is weeks to months.
Jason Wright
Jason Wright –  ‏@Astro_Wright

@MoistChure @GrnBnkTelescope @tsboyajian Timescale to publication much longer. Unless we see something obvious; then maybe not so long :)
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 12/30/2016 02:07 PM
Quote
Hello Backers,

Edit: Over the past week, a few papers were published on WTF. Jason Wright blogged about the first two, you can view that discussion here (including links to the original papers). The third paper has only been 'submitted' to the journal, meaning that it has not gone through the peer review process necessary for publication. We will discuss the contents on this once it has been accepted. Be sure to visit the sub-reddit (which now has over 4,000 subscribers) if you want to discuss more with the community. Updates to the Observations

As discussed in the last report, we have modified our observing strategies to optimize data quality. This was a concern because the image was saturating because the defocus command not properly executing. When this happened, the scatter increased in the light curve, an effect we want to minimize. To remedy this, we have now selected settings that will work whether the defocus command executes or not. Just after this change in the schedule request we were reviewing the data and saw something.

We saw the data points trending downwards - like the start of a dip. But this trend was not downwards enough to be a sure thing (it was too soon), especially if we considered the measurement errors (which is a must!). Furthermore, we only saw the downwards trend in one of the three filters at only at one of the observatory sites (what is plotted in the figure above). OK, so nothing significant, right? Right? Well, we weren't so confident about whether or not it was real because we couldn't explain what was causing the trend we observed. And if we couldn't explain the data, we couldn't let our guard down. So here we are frantically checking the LCO scheduler to see when new data was expected to be taken. If the dip trend continued at the same rate, it was the next observations that would confirm it.

At the same time we are asking ourselves hundreds of questions. Why would a trend like this appear only in one filter at one observing site? Was is astrophysical or instrumental? Did a thin layer of clouds roll in that affected the conditions? Did the image get contaminated by scattered moonlight? Did we just not understand our errors well enough? Is there some unknown source of correlated noise in the data?

And then Tyler triumphantly announced - this comparison star is BAD! It was one of the comparison stars that we have been using all along. But after the configuration change to address saturation, the conditions were just barely right (or wrong) enough to affect the one star enough to make it look like there was a dip in the data. Removing the bad comparison star fixed everything, and the data now lines up with the rest of the curve to reveal nothing but a flatline. I guess that is good. For now. We remain patient. This highlights the odd nature of astronomy (and science as a whole), occasionally things just don't work right even though they should.

On the management side of things, we are now set up with a new computer which we have named Toph. Tyler chose this name because we wanted a theme which is expandable if we ever need future computers and the computer generally won't have a monitor attached. Toph is from Avatar: The Last Airbender and is a blind, but fierce fighter. Blind, no monitor. Look, we're scientists first and good at naming things somewhere further down the list.

This is where all the data will be stored locally. Each image is about 7 megabytes in size, but throughout this campaign we will take thousands (possibly over ten thousand images). At the moment we almost have 20 GB of images! From these images we will have Toph automatically extract and produce the light curves and then email them to us and send alerts if a dipping event occurs. This is largely possible with the photometry code developed by Rachel Street and the other astronomers at LCO.

Happy holidays to you all,

~the entire WTF team Thank you once again for your support!

https://www.reddit.com/r/KIC8462852/comments/5kq58q/latest_kickstarter_post_wtf_star/
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 01/04/2017 08:38 AM
I meant that I didn't think the primary is an A star and now that I've checked, it seems to be F3V.

Not that there's anything wrong with your explanation ;)

Doh!  Why I wrote "A" eludes me ... I know it's an F.  Senility can't be ruled out :-)

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 01/04/2017 08:41 AM
Another theory:

Quote
Secular Dimming of KIC 8462852 Following its Consumption of a Planet

Quote
The Kepler-field star KIC 8462852, an otherwise apparently ordinary F3 main-sequence star, showed several highly unusual dimming events of variable depth and duration. Adding to the mystery was the discovery that KIC 8462852 faded by 14% from 1890 to 1989, as well as by another 3% over the 4 year Kepler mission. Following an initial suggestion by Wright & Sigurdsson, we propose that the secular dimming behavior is the result of the inspiral of a planetary body or bodies into KIC 8462852, which took place ~10 to 1e4 years ago (depending on the planet mass). Gravitational energy released as the body inspirals into the outer layers of the star caused a temporary and unobserved brightening, from which the stellar flux is now returning to the quiescent state. The transient dimming events could then be due to obscuration by planetary debris from an earlier partial disruption of the same inspiraling bodies, or due to evaporation and out-gassing from a tidally detached moon system. Alternatively, the dimming events could arise from a large number of bodies comet- or planetesimal-mass bodies placed onto high eccentricity orbits by the same mechanism (e.g. Lidov-Kozai oscillations due to the outer M-dwarf companion) responsible for driving the more massive planets into KIC 8462852. The required high occurrence rate of KIC 8462852-like systems which have undergone recent major planet inspiral event(s) is the greatest challenge to the model, placing large lower limits on the mass of planetary systems surrounding F stars and/or requiring an unlikely probability to catch KIC 8462852 in its current state.

https://arxiv.org/abs/1612.07332

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 01/04/2017 10:21 AM
Thing is we can keep coming up with theories on this forever but only more data is going to resolve it. So let's hope we see another dip this year or something comes out of Jason Wright's et al observing campaign.
Title: Re: Boyajians Star Updates And Discussion
Post by: savuporo on 01/04/2017 12:37 PM
Thing is we can keep coming up with theories on this forever but only more data is going to resolve it. ..
Not really. More data is going to refine the hypothesis, not resolve anything definitely
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 01/05/2017 03:01 AM
Wright's commentary on the "swallowed a planet" paper posted above http://sites.psu.edu/astrowright/2017/01/03/metzger-shen-and-stone/

It still has some loose ends, but ends up with higher marks than he gave the idea in his paper:
Quote
I’m glad to see this scenario fleshed out so well. I suspect that there are ways to save the model by finding ways to make sort of event occur more frequently—perhaps by making the merging/dips more frequent by getting a chain of material from a single massive object—so I’m optimistic there’s more to this.  I’d say this paper has moved the “post-merger return to normal” scenario from “unclear” plausibility to something like “less plausable,” or even higher.
Title: Re: Boyajians Star Updates And Discussion
Post by: TakeOff on 01/13/2017 07:22 PM
Yeah, like a planet, swallowed or crushed or whatever, covers 22% of the star's light. A star 50% larger than the Sun. Very desperate. (Please accept that it is a peryton until confirmed by a second observatory)
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 01/13/2017 08:55 PM
Yeah, like a planet, swallowed or crushed or whatever, covers 22% of the star's light.
You should probably read the paper (or at least Wright's blog post) because that's not the mechanism proposed.

edit:
And FWIW, a disrupted planet would have no trouble blocking ~22% of the stars output, the problem is doing it without infra red excess.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 01/13/2017 10:25 PM
Yeah, like a planet, swallowed or crushed or whatever, covers 22% of the star's light.
You should probably read the paper (or at least Wright's blog post) because that's not the mechanism proposed.

edit:
And FWIW, a disrupted planet would have not trouble blocking ~22% of the stars output, the problem is doing it without infra red excess.

That's why a lot of these so called explanations look bogus.
Title: Re: Boyajians Star Updates And Discussion
Post by: TakeOff on 01/14/2017 12:53 PM
Yeah, like a planet, swallowed or crushed or whatever, covers 22% of the star's light.
You should probably read the paper (or at least Wright's blog post) because that's not the mechanism proposed.

edit:
And FWIW, a disrupted planet would have not trouble blocking ~22% of the stars output, the problem is doing it without infra red excess.
The star's rotation period is about 21 hours. But somehow a planet spiraled into it and caused it to dim it by tens of percent EXACTLY every two Earth years? This is so very desperate that it is nothing but riding on the media hype by now. And we are only beginning to see Big Data coming. Soon anyone can data mine anything they have beforehand concluded that they will find. It will typically be that which is most hypable in social media. I'm glad I'm born with a BS-detector to filter this garbage!


Kepler was made to make a STATISTICAL survey of the occurrence of exoplanets. But this poor Tabby's star is now the victim of very elaborate individual interpretations from very questionable and unconfirmed data. It is taking way more attention than it deserves. It's another canali on Mars. It will backfire.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 01/15/2017 02:42 PM
The star's rotation period is about 21 hours. But somehow a planet spiraled into it and caused it to dim it by tens of percent EXACTLY every two Earth years?.

What are you talking about? The star does not dim every two years ... the dips are unpredictable with no repeat frequency.

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: TakeOff on 01/15/2017 06:05 PM
The star's rotation period is about 21 hours. But somehow a planet spiraled into it and caused it to dim it by tens of percent EXACTLY every two Earth years?.

What are you talking about? The star does not dim every two years ... the dips are unpredictable with no repeat frequency.

--- Tony

There was two Earth years between the day 792 dimming and the final set of dimmings starting day 1519. And two years earlier there was a 1% or so dimming. The malfunction was triggered regularly and caused a greater anomaly each time.
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 01/15/2017 08:54 PM
What are you talking about? The star does not dim every two years ... the dips are unpredictable with no repeat frequency.
The problems with Takeoff's theories were explained in excruciating detail in the previous thread, but the only effect appears to have been the thread getting deleted :-\ This is rather unfortunate since it had links to most of the papers about this star and some serious discussion.
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 01/15/2017 09:14 PM
Yeah, like a planet, swallowed or crushed or whatever, covers 22% of the star's light.
You should probably read the paper (or at least Wright's blog post) because that's not the mechanism proposed.

edit:
And FWIW, a disrupted planet would have not trouble blocking ~22% of the stars output, the problem is doing it without infra red excess.

That's why a lot of these so called explanations look bogus.

Yes, some of the posited explanations seem like a contrived "end state" that can be shown to somewhat model the flux dips.  However when you have to run the condition backwards in time they have difficulty creating the circumstances for the proposed event to happen, much less match observations & make testable predictions regarding future observations.
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 01/15/2017 09:20 PM
There was two Earth years between the day 792 dimming and the final set of dimmings starting day 1519. And two years earlier there was a 1% or so dimming. The malfunction was triggered regularly and caused a greater anomaly each time.

Can you describe what kind of malfunction could cause all this and why it would be triggered regularly? I sure can't.
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 01/15/2017 10:08 PM
The star's rotation period is about 21 hours. But somehow a planet spiraled into it and caused it to dim it by tens of percent EXACTLY every two Earth years?.

What are you talking about? The star does not dim every two years ... the dips are unpredictable with no repeat frequency.

--- Tony

There was two Earth years between the day 792 dimming and the final set of dimmings starting day 1519. And two years earlier there was a 1% or so dimming. The malfunction was triggered regularly and caused a greater anomaly each time.

Well clearly the difference between 1519 and 792 is not exactly two Earth years.  And the 1% dip is not another two years previous, only 652 days.

But this is irrelevant.  Kepler is on an Earth-trailing heliocentric orbit that is longer than an Earth year.  What significance is an Earth year?
Title: Re: Boyajians Star Updates And Discussion
Post by: savuporo on 01/15/2017 10:13 PM
Can you describe what kind of malfunction could cause all this and why it would be triggered regularly? I sure can't.
F-22 squadron crossing international date line comes to mind. Superficial parallel though
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 01/15/2017 11:48 PM
F-22 squadron crossing international date line comes to mind. Superficial parallel though
Would be quite a trick for a bug like that to affect one star out of ~150K.

On top of that:
1) The dimming is visible in the raw data
2) The effect was seen on more than one sensor module, but only for the one star
3) There's no obvious reason for calendar years to be relevant to the on-board processing that produces the raw data. Unlike an F-22, which has to interface extensively with human date standards, one would expect Kepler flight software to operate on some simpler system
4) As Alpha_Centauri points out, the contention that the dips are exactly 2 years apart is dubious. The 1519 and 792 dates aren't exactly 2 years apart, and they represent the deepest part of the dip, not the start of the events. The gradual start of the dimmings makes a precise start time difficult to identify.
5) The people who operate the instrument found the dimming to be consistent with real astrophysical dimming. Common defects like cosmic ray hits or changes in individual pixel sensitivity would be very obvious in the data
6) The apparent long term dimming seen by Schaefer suggests this star is undergoing some weird astrophysical behavior, and analysis of Kepler full frame engineering data by Montet & Simon appear to show a similar long term trend, once again only affecting this particular star

Again, this was almost all covered in the previous thread. It's really hard to make the case for hardware or software defects alone being responsible for the observations. That said, the raw data and instrument descriptions are all publicly available, so anyone who wants to seriously make the case should be able to do so.
Title: Re: Boyajians Star Updates And Discussion
Post by: savuporo on 01/16/2017 12:19 AM
I've read the thread, and not trying to make the case for software or hardware bugs. All I'm saying, weird stuff has been seen before

http://catb.org/esr/jargon/html/magic-story.html

Edit: and the most credible way to rule out mysterious instrument error from observation is to use another instrument.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 01/16/2017 05:54 AM
I've read the thread, and not trying to make the case for software or hardware bugs. All I'm saying, weird stuff has been seen before

http://catb.org/esr/jargon/html/magic-story.html

Edit: and the most credible way to rule out mysterious instrument error from observation is to use another instrument.

Which is what they are currently doing following their successful crowdfunding campaign,
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 01/16/2017 08:39 AM
Again, this was almost all covered in the previous thread. It's really hard to make the case for hardware or software defects alone being responsible for the observations. That said, the raw data and instrument descriptions are all publicly available, so anyone who wants to seriously make the case should be able to do so.

Indeed.  We (mostly others :-) ) spent a lot of time in the discovery paper eliminating all sorts of possible problems (including a few not mentioned here). And I've not heard anything serious questioning the astrophysical nature of the events since ...

I'm rather hoping the LCOGT campaign sees a dip and that we can bring some big instruments to bear on this weird star.

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: TakeOff on 01/16/2017 03:14 PM
What level of dimming can the telescopes now (since the Autumn of 2015, I suppose) observing this star detect? Except for the 3 deepest dips, I looks to me one would need better than 1% sensitivity to capture the last 60 days or so long pattern at the end of Kepler.

How large are the uncertainty bands for the light curve?

Except for the big dips, the sudden step down drop by ½% on day 1559 is odd. How fast did that happen, within how many minutes? And between days 1581 to 1587 the light curve suddenly has its most stable period in the entire time series. Could these be data artifacts, for example simply that the telescope did not gather any data for this star during those 6 days?

(Don't worry, since it is such a touchy issue here, for some reason, I won't bring up the hypothesis that it is a telescope problem here again, and I don't have much more to say about it anyway).
Title: Re: Boyajians Star Updates And Discussion
Post by: Ben the Space Brit on 01/16/2017 03:34 PM
At the risk of being a devil's advocate, we should avoid assuming that something falling into what seems to be a neat pattern to us is indubitably a sign of intelligence. For example, given a universe of arbitrarily large size it is actually more unlikely that there would not be at least one occasion where two completely natural phenomena take place essentially 2 yrE apart.

There is no particular compelling reason why any intelligently-generated event would fit into a multiple of some Earth-specific time-frame. Indeed, it would be more likely for any signal to be based on universal time constants such as the emission frequency of ionised hydrogen.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 01/16/2017 05:54 PM
At the risk of being a devil's advocate, we should avoid assuming that something falling into what seems to be a neat pattern to us is indubitably a sign of intelligence. For example, given a universe of arbitrarily large size it is actually more unlikely that there would not be at least one occasion where two completely natural phenomena take place essentially 2 yrE apart.

There is no particular compelling reason why any intelligently-generated event would fit into a multiple of some Earth-specific time-frame. Indeed, it would be more likely for any signal to be based on universal time constants such as the emission frequency of ionised hydrogen.

But again you're thinking like a human being, there is nothing to say that any ETI would have remotely the same frames of reference.
Title: Re: Boyajians Star Updates And Discussion
Post by: Vultur on 01/19/2017 12:49 AM
At the risk of being a devil's advocate, we should avoid assuming that something falling into what seems to be a neat pattern to us is indubitably a sign of intelligence.

I don't think anyone (any of the scientists, anyway) is saying that it's "indubitably" a sign of intelligence. But it's a natural thought when something is encountered that doesn't fit any known natural phenomenon, and all the proposed natural explanations seem to be more than a bit of a stretch.

OTOH, the problem with any ETI hypothesis is that there's no real "bounds" since we have no way to predict what an arbitrarily advanced civilization could or would do.

EDIT: And I think that this 'lack of constraints' is the real problem not its extraordinary or 'sensational' nature. I don't see any real reason to think that solar system scale engineering is 'less likely' or 'more extraordinary' than any undemonstrated astrophysical process, as we have no way to judge its likelihood.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 01/20/2017 08:13 AM
I don't think anyone (any of the scientists, anyway) is saying that it's "indubitably" a sign of intelligence.

Almost everyone is, first and foremost, considering astrophysical explanations. Though intelligent origins can't be ruled out, there is no reason to prefer them as an explanation, and such an explanation would require extraordinary evidence (which we don't have).

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 01/20/2017 03:49 PM
I don't think anyone (any of the scientists, anyway) is saying that it's "indubitably" a sign of intelligence.

Almost everyone is, first and foremost, considering astrophysical explanations. Though intelligent origins can't be ruled out, there is no reason to prefer them as an explanation, and such an explanation would require extraordinary evidence (which we don't have).

--- Tony

See this is something of a moving the goal posts statement as to why does intelligence in particular need extraordinary evidence compared to other explanations. Surely any explanation should be judged on a level playing field, not that one has to reach a higher bar anything else.
Title: Re: Boyajians Star Updates And Discussion
Post by: notsorandom on 01/20/2017 04:44 PM
Extraordinary evidence is simply evidence that can only be interpreted as being cause by ETI.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 01/20/2017 04:53 PM
Extraordinary evidence is simply evidence that can only be interpreted as being cause by ETI.

But I have the suspicion some people at least use this so they can move the goal posts so it makes proving the theory virtually impossible.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 01/20/2017 05:13 PM
New article.

http://lsuscienceblog.squarespace.com/blog/2017/1/6/tabbys-star-the-most-mysterious-star-in-the-universe
Title: Re: Boyajians Star Updates And Discussion
Post by: Robotbeat on 01/20/2017 06:57 PM
For the same reason we require extraordinary evidence that some phenomenon on Earth is caused by little elf people and not some more mundane physical explanation.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 01/20/2017 07:02 PM
For the same reason we require extraordinary evidence that some phenomenon on Earth is caused by little elf people and not some more mundane physical explanation.

That's an extremely poor comparison being as little elf people definitely don't exist but intelligent aliens possible do. And seemingly typically of the narrow thinking some take on this.
Title: Re: Boyajians Star Updates And Discussion
Post by: matthewkantar on 01/20/2017 07:25 PM
little elf people definitely don't exist

Prove it.

Matthew
Title: Re: Boyajians Star Updates And Discussion
Post by: KelvinZero on 01/20/2017 07:43 PM
That's an extremely poor comparison being as little elf people definitely don't exist but intelligent aliens possible do. And seemingly typically of the narrow thinking some take on this.
They not only could exist, they could also be aliens :-)

For me, the important part of the debate is simply that no amount of eliminating other explanations goes to proving aliens. There will always be infinite more possible explanations we haven't thought to eliminate.

Eliminating any one of these other explanations does make aliens more likely, sure, but what makes it not help as a proof is that it tells us nothing about how likely it actually is. There can't be a formula that says the probability was 0.00996, and after eliminating one thing we thought of, the chance is now 0.00997.

I think to prove aliens you have think of tests for particular types of aliens we can describe and then seeing if it passes those tests. Note that failing these tests also does nothing to disprove aliens. It could be another sort of alien we have not thought of yet. But continually passing those tests would not only become a proof of aliens, it would define the term.

Off the top of my head things that would be evidence for aliens.
* Evidence of the same phenomena spreading to neighbouring stars.
* Evidence in the spectra that suggests the dips are caused by something blocking the light that is highly abnormal chemically. Perhaps we can detect crystal or polymer, or just concentrations of certain elements that are highly unexpected from natural explanations
* Evidence of communication, obviously.
* Evidence that matches specific theories of how star-lifting or other mega engineering feats might be achieved. Just 'dips in the light that might be from something blocking it' is by itself very little.

Again, not finding these things does not quantifiably disprove aliens. Finding them would begin to build up the case for aliens though.
Title: Re: Boyajians Star Updates And Discussion
Post by: redliox on 01/21/2017 12:06 AM
Off the top of my head things that would be evidence for aliens.
* Evidence of the same phenomena spreading to neighbouring stars.
* Evidence in the spectra that suggests the dips are caused by something blocking the light that is highly abnormal chemically. Perhaps we can detect crystal or polymer, or just concentrations of certain elements that are highly unexpected from natural explanations
* Evidence of communication, obviously.
* Evidence that matches specific theories of how star-lifting or other mega engineering feats might be achieved. Just 'dips in the light that might be from something blocking it' is by itself very little.

Regarding checking neighboring stars, I'd call it 50/50.  A civilization capable of transforming their solar system into a Dyson Sphere or Ring World will both be capable of tremendous things and have a great need for resources, but interstellar travel may be hard even for them.  The physics of either warp drive or creating a wormhole already seem to imply crazy amounts of energy even a Type 2 Kardashev scale civilization may find wasteful.

All the same, comparing the system to its immediate neighbors is wise, especially if the phenomenon isn't limited to one system but is natural.  At the least we need a better look at Tabby's Star with larger telescopes.
Title: Re: Boyajians Star Updates And Discussion
Post by: KelvinZero on 01/21/2017 03:34 AM
A civilization capable of transforming their solar system into a Dyson Sphere or Ring World will both be capable of tremendous things and have a great need for resources, but interstellar travel may be hard even for them.
That is right. Failure to find these things is not the same as disproving aliens. It is finding things like this that would begin to build a case for a certain plausible type of alien. A "proof", if it were to come, would also give us a model of what these aliens are.

Real proof could tell us incredible things. For example suppose we find that really peculiar chemical spectra. In trying to figure out a model of alien that would use that, we might figure out why we would use it, and peek millions of years ahead in our own evolution. If pondering this material leads us to develop a perfect superconductor for example then that is very good evidence for intelligence there.. as it changes us here.

Proof will come simultaneously with constraining our model of our aliens to a specific thing. "Disproof", or the closest thing to it, would only come from finding a perfectly good mundane explanation that matched all our current evidence and continued to match new predictions based on that model.
Title: Re: Boyajians Star Updates And Discussion
Post by: LouScheffer on 01/21/2017 04:31 PM
Proof will come simultaneously with constraining our model of our aliens to a specific thing. "Disproof", or the closest thing to it, would only come from finding a perfectly good mundane explanation that matched all our current evidence and continued to match new predictions based on that model.
Disproof is even harder than proof.  You can imagine a pretty solid proof, such as a coherent radio signal counting out digits of PI. 

But it's hard to imagine a convincing disproof.  No amount of mundane explanations can do this, for if aliens don't want to be seen, they may arrange their affairs to look natural.  After all, camouflage is common on Earth, in biology, military, and aesthetic applications (think of cell phone towers designed to look like trees).   So a natural explanation can only suggest, but not prove, that aliens are not responsible.

The difficulty of disproof is shown by psychology experiments where they start by showing a magic trick.  Some of the audience think it's really magic, and others think it's a trick.   Then they have the magician show exactly how the trick is done, and ask the audience again.  Still not all are convinced - maybe *this time* was done by a trick, but it could be that the last time *really was* magic.  It's philosophically possible...

Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 01/22/2017 06:55 AM
But it's hard to imagine a convincing disproof.  No amount of mundane explanations can do this, for if aliens don't want to be seen, they may arrange their affairs to look natural.  After all, camouflage is common on Earth, in biology, military, and aesthetic applications (think of cell phone towers designed to look like trees).   So a natural explanation can only suggest, but not prove, that aliens are not responsible.
I would argue you can get close enough for all practical purposes. Pulsars looked like a relatively good candidate for an alien signal when they were discovered, but given what we know now, it's very clear they are natural.  It's not hard to imagine additional observations leading us to a similarly compelling, self consistent explanation for Boyajian's star.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 01/22/2017 08:22 AM
But it's hard to imagine a convincing disproof.  No amount of mundane explanations can do this, for if aliens don't want to be seen, they may arrange their affairs to look natural.  After all, camouflage is common on Earth, in biology, military, and aesthetic applications (think of cell phone towers designed to look like trees).   So a natural explanation can only suggest, but not prove, that aliens are not responsible.
I would argue you can get close enough for all practical purposes. Pulsars looked like a relatively good candidate for an alien signal when they were discovered, but given what we know now, it's very clear they are natural.  It's not hard to imagine additional observations leading us to a similarly compelling, self consistent explanation for Boyajian's star.

I think you're going to be disappointed if you think it's going to be that easy to solve this Star.
Title: Re: Boyajians Star Updates And Discussion
Post by: gospacex on 01/22/2017 12:51 PM
A civilization capable of transforming their solar system into a Dyson Sphere or Ring World will both be capable of tremendous things and have a great need for resources, but interstellar travel may be hard even for them.

Disagree. For a civilization which can do such megascale engineering, interstellar flight is nearly trivial: just build a ship big enough so that for the crew, it is no longer a vehicle they use to move from place to place, it's the place where they live. Then travel time is not a problem any more.

IOW: "spaceship Earth". (Of course, it probably can be much smaller. ~100 km asteroid-sized spacecraft/space-city should do).
Title: Re: Boyajians Star Updates And Discussion
Post by: Orbiter on 01/22/2017 12:54 PM
Off the top of my head things that would be evidence for aliens.
* Evidence of the same phenomena spreading to neighbouring stars.
* Evidence in the spectra that suggests the dips are caused by something blocking the light that is highly abnormal chemically. Perhaps we can detect crystal or polymer, or just concentrations of certain elements that are highly unexpected from natural explanations
* Evidence of communication, obviously.
* Evidence that matches specific theories of how star-lifting or other mega engineering feats might be achieved. Just 'dips in the light that might be from something blocking it' is by itself very little.

I've got one to add: direct imaging of the system. If there's really a Sol sized artificial alien megastructure orbiting this star no doubt future telescopes could resolve them (maybe as soon as JWST).
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 01/22/2017 02:09 PM
I've got one to add: direct imaging of the system. If there's really a Sol sized artificial alien megastructure orbiting this star no doubt future telescopes could resolve them (maybe as soon as JWST).

Direct imaging is still quite far from being able to do such things. JWST doesn't even come close to having enough resolution to resolve such things at ~500 pc.
Title: Re: Boyajians Star Updates And Discussion
Post by: TakeOff on 01/22/2017 03:35 PM
A civilization capable of transforming their solar system into a Dyson Sphere or Ring World will both be capable of tremendous things and have a great need for resources, but interstellar travel may be hard even for them.

Disagree. For a civilization which can do such megascale engineering, interstellar flight is nearly trivial: just build a ship big enough so that for the crew, it is no longer a vehicle they use to move from place to place, it's the place where they live. Then travel time is not a problem any more.

IOW: "spaceship Earth". (Of course, it probably can be much smaller. ~100 km asteroid-sized spacecraft/space-city should do).
Or they never die, either naturally or by technology. Then spending 100 million years in a tin can to get to Andromeda is nothing. It is pointless to speculate, based on one unstable light curve in one telescope. It is Disneyfication of "aliens". (But I think it is telling that this speculation occurs in connection to this "light curve of hope" for the SETI seekers.)
Title: Re: Boyajians Star Updates And Discussion
Post by: Patchouli on 01/22/2017 07:30 PM


Disagree. For a civilization which can do such megascale engineering, interstellar flight is nearly trivial: just build a ship big enough so that for the crew, it is no longer a vehicle they use to move from place to place, it's the place where they live. Then travel time is not a problem any more.

IOW: "spaceship Earth". (Of course, it probably can be much smaller. ~100 km asteroid-sized spacecraft/space-city should do).

Traveling to the nearest stars likely would be old hat for such a civilization.
Heck they may have even mastered relativistic ships or even some form of FTL travel.
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 01/22/2017 11:08 PM
Could we please not turn this thread into scifi speculation about alien societies.
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 01/23/2017 06:39 AM
I think you're going to be disappointed if you think it's going to be that easy to solve this Star.
I didn't mean to imply that I expect it be easy, only that it's an outcome that doesn't require any great leap of imagination: New dips detected, big telescopes pointed at it, results clearly point to some specific natural phenomena. There's a pretty long history of astronomical mysteries turning into a clear, consistent picture once some key piece of data falls into place.

Of course, there's plenty of other possible outcomes, but the point is that there are some which would effectively remove aliens from reasonable consideration.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 01/23/2017 06:51 AM
I think you're going to be disappointed if you think it's going to be that easy to solve this Star.
I didn't mean to imply that I expect it be easy, only that it's an outcome that doesn't require any great leap of imagination: New dips detected, big telescopes pointed at it, results clearly point to some specific natural phenomena. There's a pretty long history of astronomical mysteries turning into a clear, consistent picture once some key piece of data falls into place.

Of course, there's plenty of other possible outcomes, but the point is that there are some which would effectively remove aliens from reasonable consideration.

But why even try and corral an explanation down one route at this stage? After all in his last paper on the subject Jason Wright still offered a variety of possible explanations.
Title: Re: Boyajians Star Updates And Discussion
Post by: gospacex on 01/23/2017 12:45 PM


Disagree. For a civilization which can do such megascale engineering, interstellar flight is nearly trivial: just build a ship big enough so that for the crew, it is no longer a vehicle they use to move from place to place, it's the place where they live. Then travel time is not a problem any more.

IOW: "spaceship Earth". (Of course, it probably can be much smaller. ~100 km asteroid-sized spacecraft/space-city should do).

Traveling to the nearest stars likely would be old hat for such a civilization.
Heck they may have even mastered relativistic ships or even some form of FTL travel.

That assumes that there IS a way to move FTL. It may be so that laws of physics simply don't allow it.
Title: Re: Boyajians Star Updates And Discussion
Post by: Johnnyhinbos on 01/23/2017 01:47 PM
I'll add again that we're looking at 1,400 years in the past. Who knows, even if there's a Dyson sphere out there, it could be a smoldering ruin by now. Or perhaps the next thing we see is an occlusion of a near star in line but only a 100 light years from us - or perhaps we see a new star 10 light years from us and it's blue shifted, as in something's headed our way...
Title: Re: Boyajians Star Updates And Discussion
Post by: Ben the Space Brit on 01/23/2017 02:12 PM
That assumes that there IS a way to move FTL. It may be so that laws of physics simply don't allow it.

I don't know how current this is but I did see on one text book that the famous Feynman diagram suggests that travelling FTL is as easy as travelling STL; the thing forbidden by orthodox solutions of General Relativity is crossing the v=c barrier in either direction.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 03/05/2017 08:30 PM
Technical overview.

The strange star discovered by Planet Hunters

http://physicstoday.scitation.org/doi/10.1063/PT.3.3504
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 03/16/2017 06:11 PM
So if I recall correctly, the next big dip is expected to recur around April/May 2017, is that correct? And if it does recur, would that go some way in reducing the number of options for a potential solution to the mystery?

For example, if it does recur as predicted, am I right in saying that this would pretty much dismiss the idea that the blockage was caused by something in the interstellar medium? Because surely nothing in the interstellar medium would be rotating around the star in this manner? Instead some interstellar dust cloud would drift randomly, with a non-reptitive dimming pattern, right?

Also, my understanding is that with the number of telescopes now focused on this star, the next dimming event will be better analysed, with additional data gathering capabilities, allowing us to better understand the shape and substance of the intervening object?

In short, my understanding is that the mere fact that the dimming pattern repeats itself in April/May will tell us a whole lot, and then the data gathered from this dimming event (if it occurs) will provide further answers on top of that.

Am I correct?
Title: Re: Boyajians Star Updates And Discussion
Post by: gospacex on 03/16/2017 06:24 PM
That's possible. New data usually gives some new ideas.
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 03/16/2017 06:29 PM
That's possible. New data usually gives some new ideas.

My point is that there is rather a lot riding on this dimming event actually occuring as predicted. If it doesn't it would pretty much be a death blow to the idea of a locally orbiting object, and significantly strengthen the idea of a blockage in the interstellar medium instead.

So it is much more significant than just an opportunity to gather more data to form some new ideas.
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 03/16/2017 07:23 PM
So if I recall correctly, the next big dip is expected to recur around April/May 2017, is that correct?
IMHO "expected" is probably too strong a word. The case for the events being periodic is not very compelling.

Dr Boyajian's email newsletter to backers on Feb 22 addressed this:
Quote
The big dip "birthday" was Feb 21, 2017.  This date was calculated from the time difference the deepest dips in Kepler data occurred: dip on day 1519 minus dip on day 792 equals a "period" of 727 days. We then use 1519 (+ 727 + 727) to predict this event happening on Feb 21, 2017. Note: the dips on day 792 and 1519 look nothing like each other, they only have similar depths. 

Just wanted to send a short note to say that observations on Feb 21 and Feb 22 show no variation in the star's brightness.

This information, while not as exciting as detecting a dip, is still useful. It does not rule out the presence of any object in orbit, just any object with an orbital period of 727 days. In fact, if an object was on a 727 day orbital period, it would have meant that we would have seen a large dip in the start of the Kepler mission, and we did not.

Looking ahead, the dip at day 1519 was accompanied by dozens of other dips spanning at least 100 days, we may still see the star dip in the coming months and we are keeping a close eye on it.

Back to your post:
Quote
For example, if it does recur as predicted, am I right in saying that this would pretty much dismiss the idea that the blockage was caused by something in the interstellar medium?
It would probably disfavor it, but not clear it would rule it out. There are plenty of astrophysical processes which produce things that are repetitive at various scales, so if you accept filaments in the interstellar medium as a plausible cause, having them repeat is not a huge stretch. As Dr Boyajian notes, the existing data doesn't really favor a really strictly periodic signal. A repetitive structure generating a quasi-periodic signal might be a better fit (to be clear, this is my interpretation, not from Dr Boyajian)

Quote
Also, my understanding is that with the number of telescopes now focused on this star, the next dimming event will be better analysed, with additional data gathering capabilities, allowing us to better understand the shape and substance of the intervening object?
The main thing is that with monitoring, more instruments can be brought to bear if a new dimming is detected. Getting spectra during a dip should narrow things down a lot, or even resolve the mystery completely.
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 03/16/2017 07:31 PM
So if I recall correctly, the next big dip is expected to recur around April/May 2017, is that correct?
IMHO "expected" is probably too strong a word. The case for the events being periodic is not very compelling.

Dr Boyajian's email newsletter to backers on Feb 22 addressed this:
Quote
The big dip "birthday" was Feb 21, 2017.  This date was calculated from the time difference the deepest dips in Kepler data occurred: dip on day 1519 minus dip on day 792 equals a "period" of 727 days. We then use 1519 (+ 727 + 727) to predict this event happening on Feb 21, 2017. Note: the dips on day 792 and 1519 look nothing like each other, they only have similar depths. 

Just wanted to send a short note to say that observations on Feb 21 and Feb 22 show no variation in the star's brightness.

This information, while not as exciting as detecting a dip, is still useful. It does not rule out the presence of any object in orbit, just any object with an orbital period of 727 days. In fact, if an object was on a 727 day orbital period, it would have meant that we would have seen a large dip in the start of the Kepler mission, and we did not.

Looking ahead, the dip at day 1519 was accompanied by dozens of other dips spanning at least 100 days, we may still see the star dip in the coming months and we are keeping a close eye on it.

Back to your post:
Quote
For example, if it does recur as predicted, am I right in saying that this would pretty much dismiss the idea that the blockage was caused by something in the interstellar medium?
It would probably disfavor it, but not clear it would rule it out. There are plenty of astrophysical processes which produce things that are repetitive at various scales, so if you accept filaments in the interstellar medium as a plausible cause, having them repeat is not a huge stretch. As Dr Boyajian notes, the existing data doesn't really favor a really strictly periodic signal. A repetitive structure generating a quasi-periodic signal might be a better fit (to be clear, this is my interpretation, not from Dr Boyajian)

Quote
Also, my understanding is that with the number of telescopes now focused on this star, the next dimming event will be better analysed, with additional data gathering capabilities, allowing us to better understand the shape and substance of the intervening object?
The main thing is that with monitoring, more instruments can be brought to bear if a new dimming is detected. Getting spectra during a dip should narrow things down a lot, or even resolve the mystery completely.

Thank you. That clarifies a lot for me. I'm not sure where I got the April/May dip expectation from then. And if the dips are in fact not strictly repetitive, what type of orbiting body could produce such a pattern? Something that changes orbital speed? Or perhaps multiple overlapping objects that only align occasionally?

Anyway, it would be rather disappointing if no dips occur ever again. The whole thing would then just fizzle out and remain a mystery, similar to the SETI "WOW" signal some decades ago.
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 03/16/2017 08:20 PM
Thank you. That clarifies a lot for me. I'm not sure where I got the April/May dip expectation from then.
Dr. Boyajian gives a ~100 day window starting at the end of February, so April/May could have come from someone picking the midpoint or end instead. Again, the "period" is pretty fuzzy, because the episodes of dips last varying amounts of time and the boundaries aren't well defined.
Quote
And if the dips are in fact not strictly repetitive, what type of orbiting body could produce such a pattern? Something that changes orbital speed?
The existing data already rules out single or small numbers of solid objects with a very high degree of confidence.

The original comet swarm hypothesis might be able to do it: We might only see the activity when a particularly large one disintegrates, or they might be on a much longer orbit with the ~700 day interval produced by spacing between bodies sharing the orbit e.g. due to break up on a previous orbit.

The "alien megastructure" idea can do it, because aliens can do whatever they want... or less glibly, it assumes vast swarms of objects possibly under active control, so getting periodic but variable groupings is not a stretch.

None of this is particularly satisfactory, but it's not completely unphysical ;)
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 03/20/2017 07:34 PM
K2 finds 23 more stars with unusual dips in their light curves.

Quote
The primary Kepler mission provided light curves for over 100,000 stars, and its continuation K2 is observing another 20,000 stars every three months. As we enter an era where these enormous photometric data sets become commonplace — Gaia will obtain photometry for millions of stars, and LSST billions — it’s crucial that we understand the different categories of variability observed in these stars.

The authors find three different types of light curves among their 23 unusual stars. Scallop-shell curves (top) show many undulations; persistent flux-dip class curves (middle) have discrete triangularly shaped flux dips; transient, narrow dip class curves (bottom) have only one dip that is variable in depth. The authors speculate a common cause for the scallop-shell and persistent flux-dip stars, and a different cause for the transient flux-dip stars. [Stauffer et al. 2017]
After filtering out the stars with planets, those in binary systems, those with circumstellar disks, and those with starspots, a number of oddities remain: a menagerie of stars with periodic variability that can’t be accounted for in these categories. Some of these stars are now famous (for instance, Boyajian’s star); some are lesser known. But by continuing to build up this sample of stars with unusual light curves, we have a better chance of understanding the sources of variability.

http://aasnova.org/2017/03/17/more-unusual-light-curves-from-kepler
Title: Re: Boyajians Star Updates And Discussion
Post by: Ben the Space Brit on 03/21/2017 12:34 PM
If these other objects turn out to have the same family of spectral type, similar light curves and the same overall behaviour, I desperately hope that the IAU calls them 'Tabby-class Variables'.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 03/22/2017 08:41 AM
Unlikely, the group of 23 stars are all very very young and the dips are consistent with still-forming systems.
Tabby's star is respectably middle aged and these causes are pretty much ruled out.

But a nice thought :-)

---Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Proponent on 03/22/2017 10:10 AM
For the same reason we require extraordinary evidence that some phenomenon on Earth is caused by little elf people and not some more mundane physical explanation.

That's an extremely poor comparison being as little elf people definitely don't exist but intelligent aliens possible do. And seemingly typically of the narrow thinking some take on this.

ISTM it's ultimately an application of Occam's Razor.  An explanation involving intelligence introduces a huge number of degrees of freedom and limits predictive power.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 03/22/2017 10:29 AM
For the same reason we require extraordinary evidence that some phenomenon on Earth is caused by little elf people and not some more mundane physical explanation.

That's an extremely poor comparison being as little elf people definitely don't exist but intelligent aliens possible do. And seemingly typically of the narrow thinking some take on this.

ISTM it's ultimately an application of Occam's Razor.  An explanation involving intelligence introduces a huge number of degrees of freedom and limits predictive power.

That's an ineffective argument against it though as it saying because this is hard to predict then it cannot be the answer.
Title: Re: Boyajians Star Updates And Discussion
Post by: Proponent on 03/22/2017 10:57 AM
I'm not saying the difficulty in predicting the phenomenon in the first place is the problem, I'm saying that it's difficult to make testable predictions on the basis of an explanation involving intelligent life, because if a prediction doesn't pan out, you can probably say, "Oh well, I guess they made a different decision than the one I expected."  There are too many degrees of freedom.

To put it another way, given a large number of free variables, I can fit just about any model to any set of observations.  So, the fact that I've managed to fit a very complicated model to the observations give me very little confidence in the model.  Life, especially intelligent life, involves a very large number of degrees of freedom, so we should be very skeptical of the likelihood of an explanation involving intelligent life, unless the data are truly overwhelming.

In the context of the scientific method, simpler theories and those with greater predictive are to be preferred.  One reason for preferring predictive power is that it makes theories more testable, and testability is central to the scientific method.

A more practical reason for a scientist to prefer natural explanations is that explanations involving extraterrestrial life have poor track records:

* The canals of Mars;
* The vegetation hypothesis for the seasonal changes in Mars' coloration;
* The suggestion that Mars' moons were artificial, because the large decay rates of their orbits (which were inaccurately determined) implied very low densities;
* The LGM hypothesis for pulsars; and
* The suggestion that quasars were the exhaust plumes of starship engines (the lack of blue-shifted quasars be explained by the paucity of UV observations at the time).

(Can anybody think of any more examples?)

Explanations involving life are emotionally appealing, and there's nothing wrong with discussing them.  But I think we need guard against that appeal clouding our judgments as to their likelihoods.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 03/22/2017 03:07 PM
I'm not saying the difficulty in predicting the phenomenon in the first place is the problem, I'm saying that it's difficult to make testable predictions on the basis of an explanation involving intelligent life, because if a prediction doesn't pan out, you can probably say, "Oh well, I guess they made a different decision than the one I expected."  There are too many degrees of freedom.

To put it another way, given a large number of free variables, I can fit just about any model to any set of observations.  So, the fact that I've managed to fit a very complicated model to the observations give me very little confidence in the model.  Life, especially intelligent life, involves a very large number of degrees of freedom, so we should be very skeptical of the likelihood of an explanation involving intelligent life, unless the data are truly overwhelming.

In the context of the scientific method, simpler theories and those with greater predictive are to be preferred.  One reason for preferring predictive power is that it makes theories more testable, and testability is central to the scientific method.

A more practical reason for a scientist to prefer natural explanations is that explanations involving extraterrestrial life have poor track records:

* The canals of Mars;
* The vegetation hypothesis for the seasonal changes in Mars' coloration;
* The suggestion that Mars' moons were artificial, because the large decay rates of their orbits (which were inaccurately determined) implied very low densities;
* The LGM hypothesis for pulsars; and
* The suggestion that quasars were the exhaust plumes of starship engines (the lack of blue-shifted quasars be explained by the paucity of UV observations at the time).

(Can anybody think of any more examples?)

Explanations involving life are emotionally appealing, and there's nothing wrong with discussing them.  But I think we need guard against that appeal clouding our judgments as to their likelihoods.

But then that still is ineffective argument because that then creates an inherent bias towards natural explanations. An effective argument should have no bias at all in the scientific method. There was an interesting discussion recently that scientific papers that came in from SETI were seemingly being rejected more often from publication and the argument put forward by some to explain this was there is an inherent bias by editors to anything that might include any kind of discussion of ETI.
Title: Re: Boyajians Star Updates And Discussion
Post by: JasonAW3 on 03/22/2017 07:55 PM
Odd thought here;

      Is it possible that what we are seeing with the dips in luminosity are from multiple clouds of debris, in different orbits and with different orbital inclinations?

      In other words; is it possible that the big dip we saw the last time was a coincidental alignment of multiple debris clouds in different orbits, that just happened to align together between us and Boyajian's star?  This would explain a semi-periodic nature of the various dips we are seeing.

      But it does pose another interesting question;  If the dips are caused by multiple debris clouds in different orbits, what caused the debris clouds to form in the first place?
Title: Re: Boyajians Star Updates And Discussion
Post by: CuddlyRocket on 03/22/2017 09:40 PM
There was an interesting discussion recently that scientific papers that came in from SETI were seemingly being rejected more often from publication and the argument put forward by some to explain this was there is an inherent bias by editors to anything that might include any kind of discussion of ETI.

Too many kooks have spoiled the broth!
Title: Re: Boyajians Star Updates And Discussion
Post by: Proponent on 03/23/2017 09:23 AM
But then that still is ineffective argument because that then creates an inherent bias towards natural explanations. An effective argument should have no bias at all in the scientific method. There was an interesting discussion recently that scientific papers that came in from SETI were seemingly being rejected more often from publication and the argument put forward by some to explain this was there is an inherent bias by editors to anything that might include any kind of discussion of ETI.

If you follow the scientific paradigm, the repeating cycle of hypothesis and test, it is rational to prefer simple explanations.  To put it in more colloquial terms, extraordinary claims require extraordinary evidence.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 03/23/2017 09:24 AM
But then that still is ineffective argument because that then creates an inherent bias towards natural explanations. An effective argument should have no bias at all in the scientific method. There was an interesting discussion recently that scientific papers that came in from SETI were seemingly being rejected more often from publication and the argument put forward by some to explain this was there is an inherent bias by editors to anything that might include any kind of discussion of ETI.

If you follow the scientific paradigm, the repeating cycle of hypothesis and test, it is rational to prefer simple explanations.  To put it in more colloquial terms, extraordinary claims require extraordinary evidence.

Which again is just a form of moving the goalposts.
Title: Re: Boyajians Star Updates And Discussion
Post by: ChrisWilson68 on 03/23/2017 09:43 AM
But then that still is ineffective argument because that then creates an inherent bias towards natural explanations. An effective argument should have no bias at all in the scientific method. There was an interesting discussion recently that scientific papers that came in from SETI were seemingly being rejected more often from publication and the argument put forward by some to explain this was there is an inherent bias by editors to anything that might include any kind of discussion of ETI.

If you follow the scientific paradigm, the repeating cycle of hypothesis and test, it is rational to prefer simple explanations.  To put it in more colloquial terms, extraordinary claims require extraordinary evidence.

No.  You are equating two very different things.  Extraordinary claims requiring extraordinary evidence is about a claim for something that violates a principle for which there is a large amount of good evidence.  It is not about whether a given theory is simple or complex.

It is not logical to prefer a simple mechanism over a complex mechanism for a physical phenomenon.  What is logical is to prefer a theory that has a lot of evidence over one that has little evidence.

In the case of Tabby's Star, there is no good evidence against the idea of alien megastructures around this world, and no good evidence for any particular theory, so the "extraordinary claims require extraordinary evidence" rule does not apply.

Title: Re: Boyajians Star Updates And Discussion
Post by: gospacex on 03/23/2017 10:22 AM
No.  You are equating two very different things.  Extraordinary claims requiring extraordinary evidence is about a claim for something that violates a principle for which there is a large amount of good evidence.

Wrong.
I'll give an example.

If I'd claim that I have a house, people wouldn't have serious reasons to not believe me, and "ordinary" evidence of it, such as a few photos of me and the house, would do.

If I'd claim that I have a house with a garage with a functioning gravitic interstellar starship inside, a few photos of me with that "starship" would not convince anyone.
Title: Re: Boyajians Star Updates And Discussion
Post by: ChrisWilson68 on 03/23/2017 10:32 AM
No.  You are equating two very different things.  Extraordinary claims requiring extraordinary evidence is about a claim for something that violates a principle for which there is a large amount of good evidence.

Wrong.
I'll give an example.

If I'd claim that I have a house, people wouldn't have serious reasons to not believe me, and "ordinary" evidence of it, such as a few photos of me and the house, would do.

If I'd claim that I have a house with a garage with a functioning gravitic interstellar starship inside, a few photos of me with that "starship" would not convince anyone.

Your so-called example doesn't help your case at all, because it's not remotely similar.

In your example, there's no data that is unexplained and in need of a theory to explain it.  On the contrary, there is plenty of evidence that it would be unlikely for humans to have interstellar sharships in their garage, and plenty of evidence that people often lie.  So, the lie is the far more likely explanation, because it's what's supported by the evidence.

There's no evidence either way for what is causing the observed light curve at Taby's Star, and no evidence against the idea that alien intelligence is present in the solar systems of some stars.
Title: Re: Boyajians Star Updates And Discussion
Post by: gospacex on 03/23/2017 10:39 AM
No.  You are equating two very different things.  Extraordinary claims requiring extraordinary evidence is about a claim for something that violates a principle for which there is a large amount of good evidence.

Wrong.
I'll give an example.

If I'd claim that I have a house, people wouldn't have serious reasons to not believe me, and "ordinary" evidence of it, such as a few photos of me and the house, would do.

If I'd claim that I have a house with a garage with a functioning gravitic interstellar starship inside, a few photos of me with that "starship" would not convince anyone.

Your so-called example doesn't help your case at all, because it's not remotely similar.

In your example, there's no data that is unexplained and in need of a theory to explain it.  On the contrary, there is plenty of evidence that it would be unlikely for humans to have interstellar sharships in their garage, and plenty of evidence that people often lie.  So, the lie is the far more likely explanation, because it's what's supported by the evidence.

There's no evidence either way for what is causing the observed light curve at Taby's Star, and no evidence against the idea that alien intelligence is present in the solar systems of some stars.

I can easily use your argument against "alien structure" claim:

"There is plenty of evidence that it would be unlikely for any alien artificial structures to be seen anywhere, and plenty of evidence that variable star types are abundant."

Specifically, by now there are some 50 different types of variable stars known. Considering that they were identified during only some 150 years, it means on average a new variable star type is identified every 3 years.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 03/23/2017 12:33 PM
No.  You are equating two very different things.  Extraordinary claims requiring extraordinary evidence is about a claim for something that violates a principle for which there is a large amount of good evidence.

Wrong.
I'll give an example.

If I'd claim that I have a house, people wouldn't have serious reasons to not believe me, and "ordinary" evidence of it, such as a few photos of me and the house, would do.

If I'd claim that I have a house with a garage with a functioning gravitic interstellar starship inside, a few photos of me with that "starship" would not convince anyone.

Your so-called example doesn't help your case at all, because it's not remotely similar.

In your example, there's no data that is unexplained and in need of a theory to explain it.  On the contrary, there is plenty of evidence that it would be unlikely for humans to have interstellar sharships in their garage, and plenty of evidence that people often lie.  So, the lie is the far more likely explanation, because it's what's supported by the evidence.

There's no evidence either way for what is causing the observed light curve at Taby's Star, and no evidence against the idea that alien intelligence is present in the solar systems of some stars.

I can easily use your argument against "alien structure" claim:

"There is plenty of evidence that it would be unlikely for any alien artificial structures to be seen anywhere, and plenty of evidence that variable star types are abundant."

Specifically, by now there are some 50 different types of variable stars known. Considering that they were identified during only some 150 years, it means on average a new variable star type is identified every 3 years.

There are too many unknown variables at this stage. How would we know what aliens do or don't do. It's just as likely that it is a limit of our current observational  technology as to why we haven't detected ETIs as anything else. It's like in the fifties where all the moons of Jupiter were assumed to be lifeless chunks of rock it wasn't until our technology improved we discovered they weren't.

Your argument just flags up a temporal arrogance over our current level of understanding and technology.
Title: Re: Boyajians Star Updates And Discussion
Post by: notsorandom on 03/23/2017 01:10 PM
In the case of Tabby's Star, there is no good evidence against the idea of alien megastructures around this world, and no good evidence for any particular theory, so the "extraordinary claims require extraordinary evidence" rule does not apply.
There is good evidence against the alien megastructures hypothesis, the lack of IR excess. Energy collectors blocking that much light would reradiate an amount of IR detectable by WISE and other telescopes yet we don't seen that IR. The classic Dyson Swarm doesn't fit the already observed data. For the aliens to still be a hypothesis they need to have either built a thin disk of collectors exactly edge on to us, be directing the energy into a beam to power a light sail or something like that, or have figured out a way to break thermodynamics.

As more observations are made the ETI hypothesis may get further constrained and thus require the aliens to be doing doing weirder and more exotic things to still be able to fit with the data. The objection that people have with aliens as an explanation is that aliens can be hypothesized do arbitrarily weird and exotic things. At what point do we say we are expecting the aliens to be doing too much to take that hypothesis out of contention?
Title: Re: Boyajians Star Updates And Discussion
Post by: Proponent on 03/23/2017 03:14 PM
It is not logical to prefer a simple mechanism over a complex mechanism for a physical phenomenon.  What is logical is to prefer a theory that has a lot of evidence over one that has little evidence.

Given a two data points, would you fit a straight line to them or a parabola, cubic or higher-order polynomial?  They will all fit the data perfectly.
Title: Re: Boyajians Star Updates And Discussion
Post by: llanitedave on 03/23/2017 03:33 PM
It is not logical to prefer a simple mechanism over a complex mechanism for a physical phenomenon.  What is logical is to prefer a theory that has a lot of evidence over one that has little evidence.

Given a two data points, would you fit a straight line to them or a parabola, cubic or higher-order polynomial?  They will all fit the data perfectly.


Exactly.  It is always preferable to choose the simpler solution over the complex one, with the caveat that the simpler solution also accommodates all observed data.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 03/23/2017 07:12 PM
In the case of Tabby's Star, there is no good evidence against the idea of alien megastructures around this world, and no good evidence for any particular theory, so the "extraordinary claims require extraordinary evidence" rule does not apply.
There is good evidence against the alien megastructures hypothesis, the lack of IR excess. Energy collectors blocking that much light would reradiate an amount of IR detectable by WISE and other telescopes yet we don't seen that IR. The classic Dyson Swarm doesn't fit the already observed data. For the aliens to still be a hypothesis they need to have either built a thin disk of collectors exactly edge on to us, be directing the energy into a beam to power a light sail or something like that, or have figured out a way to break thermodynamics.

As more observations are made the ETI hypothesis may get further constrained and thus require the aliens to be doing doing weirder and more exotic things to still be able to fit with the data. The objection that people have with aliens as an explanation is that aliens can be hypothesized do arbitrarily weird and exotic things. At what point do we say we are expecting the aliens to be doing too much to take that hypothesis out of contention?

Its entirely possible that to our limited knowledge they maybe doing weird and exotic things. Would you expect ants to understand what we are doing?
Title: Re: Boyajians Star Updates And Discussion
Post by: Phil Stooke on 03/23/2017 07:22 PM
"Would you expect ants to understand what we are doing?"

Well, no... but as a well-educated academic ant I wouldn't rely on 'magic human' to explain everything I didn't yet understand.  Aliens are always going to be a possibility, but it's not a good idea to rely on them as an explanation for anything.  More likely, we just haven't figured out the non-alien explanation... yet.
Title: Re: Boyajians Star Updates And Discussion
Post by: gospacex on 03/23/2017 11:39 PM
No.  You are equating two very different things.  Extraordinary claims requiring extraordinary evidence is about a claim for something that violates a principle for which there is a large amount of good evidence.

Wrong.
I'll give an example.

If I'd claim that I have a house, people wouldn't have serious reasons to not believe me, and "ordinary" evidence of it, such as a few photos of me and the house, would do.

If I'd claim that I have a house with a garage with a functioning gravitic interstellar starship inside, a few photos of me with that "starship" would not convince anyone.

Your so-called example doesn't help your case at all, because it's not remotely similar.

In your example, there's no data that is unexplained and in need of a theory to explain it.  On the contrary, there is plenty of evidence that it would be unlikely for humans to have interstellar sharships in their garage, and plenty of evidence that people often lie.  So, the lie is the far more likely explanation, because it's what's supported by the evidence.

There's no evidence either way for what is causing the observed light curve at Taby's Star, and no evidence against the idea that alien intelligence is present in the solar systems of some stars.

I can easily use your argument against "alien structure" claim:

"There is plenty of evidence that it would be unlikely for any alien artificial structures to be seen anywhere, and plenty of evidence that variable star types are abundant."

Specifically, by now there are some 50 different types of variable stars known. Considering that they were identified during only some 150 years, it means on average a new variable star type is identified every 3 years.

There are too many unknown variables at this stage. How would we know what aliens do or don't do. It's just as likely that it is a limit of our current observational  technology as to why we haven't detected ETIs as anything else. It's like in the fifties where all the moons of Jupiter were assumed to be lifeless chunks of rock it wasn't until our technology improved we discovered they weren't.

Your argument just flags up a temporal arrogance over our current level of understanding and technology.

You completely misunderstood my argument.
I gave a real-world example why extraordinary claim ("I have a starship") requires extraordinary evidence to be accepted, whereas a mundane one ("I have a house") does not.
I did not say anything at all about our understanding of possible aliens.
I'm saying that "it's aliens!" is an extraordinary claim.
Title: Re: Boyajians Star Updates And Discussion
Post by: notsorandom on 03/24/2017 04:02 PM
Its entirely possible that to our limited knowledge they maybe doing weird and exotic things. Would you expect ants to understand what we are doing?
There is a difference between not knowing something and not knowing how to figure it out. There are things that neither humans or ants know, yet humans have the ability to figure those things out. In that way we have much more cognitively in common with an alien building megastructures than an ant.

Any scientific hypothesis has to account for all the observations and data as well as be falsifiable. Aliens acting beyond our comprehension can fit all the observations one could possibly make about this star. For example what if we see another dimming event and it is not achromatic, that shorter wavelengths get blocked preferentially. The simple natural explanation is that dust is blocking the light. It could very well be that aliens, for what a reason we can't understand, are blocking the light in a way that make it look like dust to us. What if we see other stars that are far away from this one but angularly close in the field of view dimming? The simple natural explanation is that there is something in the interstellar medium between here and there. Yet we could say that the aliens are building structures around those stars too. So we can't ever rule out aliens being behind what we are seeming but we also can't rule out unicorns being the culprits too.

We can however put specific constraints on aliens, make those scenarios falsifiable, and then test them. We know that there are only some many ways it makes sense to build an structure around a star for energy collection. We can model what they would be made out of, where they would be, and what it would look like. From that we can say these are the things we would expect to see from each of these configurations. If we see something that doesn't fit the models then we can say those specific type of aliens are ruled out.
Title: Re: Boyajians Star Updates And Discussion
Post by: TakeOff on 04/01/2017 03:48 AM
One way to generate the sharp V-shaped dips in the light curve is to have an elongated object transit it that is exactly one stellar diameter long. Isn't that a strong argument that if this is an astrophysical phenomena, it is happening on the surface of the star since the diameter is a property of the star? What explanations are there for the V-shapes?
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 04/01/2017 08:35 PM
Isn't that a strong argument that if this is an astrophysical phenomena, it is happening on the surface of the star since the diameter is a property of the star? What explanations are there for the V-shapes?
1) The dips aren't really V shaped. They are complex and asymmetric. The one around 792 is kinda V shaped, but it's still rather asymmetric and an explanation that only accounts for one event in the series isn't very satisfactory.
2) Pretty much all the viable explanations that involve something between us and the star (as opposed to intrinsic variability) invoke a diffuse object. Producing the observed light curve with a cloud of varying density doesn't require anything special.
3) Star spots are not a good fit, for reasons explained by Jason Wright in http://sites.psu.edu/astrowright/2016/09/03/what-could-be-going-on-with-boyajians-star-part-ix-intrinsic-variations/

I highly recommend reading Dr Wrights post on this topic and/or the associated paper to get an idea of ideas that are realistically in play.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 04/01/2017 09:50 PM
I will just leave this here and make of it what you will of the responses to a question I would have asked myself.

https://www.reddit.com/r/KIC8462852/comments/62kuct/why_havent_we_received_a_gbt_update/

Might be worth a little look.

https://disownedsky.blogspot.co.uk/2017/03/brute-force-and-aavso-data-on-boyajians.html?m=1
Title: Re: Boyajians Star Updates And Discussion
Post by: TakeOff on 04/01/2017 10:06 PM
Isn't that a strong argument that if this is an astrophysical phenomena, it is happening on the surface of the star since the diameter is a property of the star? What explanations are there for the V-shapes?
1) The dips aren't really V shaped. They are complex and asymmetric. The one around 792 is kinda V shaped, but it's still rather asymmetric and an explanation that only accounts for one event in the series isn't very satisfactory.
2) Pretty much all the viable explanations that involve something between us and the star (as opposed to intrinsic variability) invoke a diffuse object. Producing the observed light curve with a cloud of varying density doesn't require anything special.
3) Star spots are not a good fit, for reasons explained by Jason Wright in http://sites.psu.edu/astrowright/2016/09/03/what-could-be-going-on-with-boyajians-star-part-ix-intrinsic-variations/

I highly recommend reading Dr Wrights post on this topic and/or the associated paper to get an idea of ideas that are realistically in play.
The dips are actually really very V-shaped! Have a look if you don't believe me.
Otherwise I agree with your conclusions. Kepler simply suffered a malfunction. There's no possible physical explanation between the star and the telescope. The error is between the telescope and us. Wright's written ideas come into play the day when a second telescope confirmes Tabby's star's deep excursions. Kind of waiting. And still waiting. Is there some defined bottom limit for defining a failure?
Title: Re: Boyajians Star Updates And Discussion
Post by: RonM on 04/01/2017 10:39 PM
Isn't that a strong argument that if this is an astrophysical phenomena, it is happening on the surface of the star since the diameter is a property of the star? What explanations are there for the V-shapes?
1) The dips aren't really V shaped. They are complex and asymmetric. The one around 792 is kinda V shaped, but it's still rather asymmetric and an explanation that only accounts for one event in the series isn't very satisfactory.
2) Pretty much all the viable explanations that involve something between us and the star (as opposed to intrinsic variability) invoke a diffuse object. Producing the observed light curve with a cloud of varying density doesn't require anything special.
3) Star spots are not a good fit, for reasons explained by Jason Wright in http://sites.psu.edu/astrowright/2016/09/03/what-could-be-going-on-with-boyajians-star-part-ix-intrinsic-variations/

I highly recommend reading Dr Wrights post on this topic and/or the associated paper to get an idea of ideas that are realistically in play.
The dips are actually really very V-shaped! Have a look if you don't believe me.
Otherwise I agree with your conclusions. Kepler simply suffered a malfunction. There's no possible physical explanation between the star and the telescope. The error is between the telescope and us. Wright's written ideas come into play the day when a second telescope confirmes Tabby's star's deep excursions. Kind of waiting. And still waiting. Is there some defined bottom limit for defining a failure?

http://sites.psu.edu/astrowright/2016/08/31/what-could-be-going-on-with-boyajians-star-part-iv-nearby-stars-instrumental-effects-and-a-solar-system-cloud/ (http://sites.psu.edu/astrowright/2016/08/31/what-could-be-going-on-with-boyajians-star-part-iv-nearby-stars-instrumental-effects-and-a-solar-system-cloud/)

Quote
Hypothesis 1) It’s Instrumental

That is, there is no dimming to explain, it’s an artifact of the instruments.  Dr. Boyajian ruled this out in her paper regarding the dips, and since then many groups have gone back to the Kepler data to see if they can find a problem, including Kepler team members.  The dips are real.

The long-term dimming Schaefer sees could be instrumental — indeed there was a big food-fight over this issue, but, as I wrote in Part I, the Montet & Simon discovery of similar dimming during the Kepler mission (and careful use of control stars) provides independent confirmation of the phenomenon.

I think we can put this one to bed.  Subjective verdict: very unlikely
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 04/01/2017 11:12 PM
The dips are actually really very V-shaped! Have a look if you don't believe me.
I have looked at these light curves quite a bit. All I can say is you have a very different idea of "v-shaped" than I do. Attached is figure 1 from the original Boyajian et al paper (https://arxiv.org/abs/1509.03622).
Quote
Otherwise I agree with your conclusions. Kepler simply suffered a malfunction.
This is most definitely not my conclusion. Wright and virtually every other professional who has weighed in on the subject rate instrumental error as a very unlikely explanation. I see no reason to disagree with them, and AFAIK no one has put forward a scenario involving instrumental error which is consistent with the data.
Quote
There's no possible physical explanation between the star and the telescope.
This is not correct.  Wright's review offers several, and others have been published since. Most of them are somewhat unsatisfactory because they require coincidences or phenomena we aren't sure exist, but they aren't un-physical.

If you are really interested in the subject, I'd highly recommend reading the published literature.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 04/02/2017 08:20 AM
Isn't that a strong argument that if this is an astrophysical phenomena, it is happening on the surface of the star since the diameter is a property of the star? What explanations are there for the V-shapes?
1) The dips aren't really V shaped. They are complex and asymmetric. The one around 792 is kinda V shaped, but it's still rather asymmetric and an explanation that only accounts for one event in the series isn't very satisfactory.
2) Pretty much all the viable explanations that involve something between us and the star (as opposed to intrinsic variability) invoke a diffuse object. Producing the observed light curve with a cloud of varying density doesn't require anything special.
3) Star spots are not a good fit, for reasons explained by Jason Wright in http://sites.psu.edu/astrowright/2016/09/03/what-could-be-going-on-with-boyajians-star-part-ix-intrinsic-variations/

I highly recommend reading Dr Wrights post on this topic and/or the associated paper to get an idea of ideas that are realistically in play.
The dips are actually really very V-shaped! Have a look if you don't believe me.
Otherwise I agree with your conclusions. Kepler simply suffered a malfunction. There's no possible physical explanation between the star and the telescope. The error is between the telescope and us. Wright's written ideas come into play the day when a second telescope confirmes Tabby's star's deep excursions. Kind of waiting. And still waiting. Is there some defined bottom limit for defining a failure?

The rumour goes that there will be results from other observatories which will end this kind of speculation, as that's been the inference when others have made similar mistaken speculations.
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 04/02/2017 09:27 AM
The rumour goes that there will be results from other observatories which will end this kind of speculation, as that's been the inference when others have made similar mistaken speculations.

Can you clarify what the rumours are saying?
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 04/02/2017 09:29 AM
The rumour goes that there will be results from other observatories which will end this kind of speculation, as that's been the inference when others have made similar mistaken speculations.

Can you clarify what the rumours are saying?

Look on the first link I posted in my post directly before the one you've quoted here. Before you ask yes it's very vague but that's not surprising in the circumstances. You'll also need to follow the link within the link.
Title: Re: Boyajians Star Updates And Discussion
Post by: TakeOff on 04/02/2017 12:32 PM
Okay, with v-shape I mean the sharp bottom. The shadowing never remains constant. The asymmetries around is another big headache. The light curve has sharp dips that are suddenly cut off by a sharp rise. Is this characteristic for signals generated by electrical glitches?


The very clean dip two years before the mess at the end of the light curve must really make it all more challenging to explain. So it wasn't a one off event, but something that happens every other year or so. Once as a clean signal and later repeated with similar shape and amplitude but embedded in noise.


What confidence intervals should one have in mind when looking at the light curve in Boyajian's paper? How good is the time resolution of the dips, could it be that they went down to zero for a few seconds?


Day 1559 the light curve in the paper is suddenly cut by half of a percent, when it reaches its highest level and during an otherwise calm period. Apparently some kind of recalibration. It makes me wonder about the 100 year and 4 year dimmings, how well calibrated they are. If one suddenly shifts the entire light curve by half of a percent every other year one might make up any kind of funny correlations. Or maybe there's no data because the curve looks flat before that drop? There are a couple of longer periods with flat curves, is there no data about potential dips there too? Like around day 805 just after the first clean big one.


What about the upside here? After day 1528 the star is up to almost 1% brighter than the normalized average. And not in any transiting manner. What could brighten a huge F-star like that by half of a percent steadily for two weeks? Or is the normalization off?
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 04/02/2017 01:37 PM
Okay, with v-shape I mean the sharp bottom. The shadowing never remains constant. The asymmetries around is another big headache. The light curve has sharp dips that are suddenly cut off by a sharp rise. Is this characteristic for signals generated by electrical glitches?

No, as has been said repeatedly, instrumental errors have been pretty much eliminated as an explanation.  It was looked at very seriously, and the curve matches no conceivable fault.

The space craft rotated 90 degrees every quarter, such that each target star is on a different CCD module, in a different orientation. Which means not only that different pixels are collected, but the optimal aperture for wach quarter is different as well. So any fault would have to affect *only* the pixels in the optimal aperture on 4 different CCDs and not affect any adjacent pixels.

Quote
What confidence intervals should one have in mind when looking at the light curve in Boyajian's paper? How good is the time resolution of the dips, could it be that they went down to zero for a few seconds?

No. The CCD pixels collect flux for 30 minutes (in long cadence). Then an overall flux value is created from a set of aperture pixels selected from the current pixel centroid and point spread function.

Quote
Day 1559 the light curve in the paper is suddenly cut by half of a percent, when it reaches its highest level and during an otherwise calm period. Apparently some kind of recalibration. It makes me wonder about the 100 year and 4 year dimmings, how well calibrated they are. If one suddenly shifts the entire light curve by half of a percent every other year one might make up any kind of funny correlations. Or maybe there's no data because the curve looks flat before that drop? There are a couple of longer periods with flat curves, is there no data about potential dips there too? Like around day 805 just after the first clean big one.

The processing of the curve (PDCSAP pipeline) is intended for transit detection and produces artefacts like that as a natural consequence of the processing - essentially the algorithm corrects for pointing errors and removes a moving-median from the curve (it is much more complex, but that is the essence), then normalises the values to "1".

When looking at absolute flux, this curve (though easily accessible) is NOT reliable, and you need to calibrate against the full frame images (and other stuff).

Quote
What about the upside here? After day 1528 the star is up to almost 1% brighter than the normalized average. And not in any transiting manner. What could brighten a huge F-star like that by half of a percent steadily for two weeks? Or is the normalization off?

As above, this is a direct consequence of the correction pipeline and is not real (think how a moving median removal behave when there is a massive prolonged dip).

As hop suggested, if you are serious, you need to learn how the instrument actually works and how it can fail.

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 04/02/2017 02:56 PM
Okay, with v-shape I mean the sharp bottom. The shadowing never remains constant. The asymmetries around is another big headache. The light curve has sharp dips that are suddenly cut off by a sharp rise. Is this characteristic for signals generated by electrical glitches?

No, as has been said repeatedly, instrumental errors have been pretty much eliminated as an explanation.  It was looked at very seriously, and the curve matches no conceivable fault.

The space craft rotated 90 degrees every quarter, such that each target star is on a different CCD module, in a different orientation. Which means not only that different pixels are collected, but the optimal aperture for wach quarter is different as well. So any fault would have to affect *only* the pixels in the optimal aperture on 4 different CCDs and not affect any adjacent pixels.

Quote
What confidence intervals should one have in mind when looking at the light curve in Boyajian's paper? How good is the time resolution of the dips, could it be that they went down to zero for a few seconds?

No. The CCD pixels collect flux for 30 minutes (in long cadence). Then an overall flux value is created from a set of aperture pixels selected from the current pixel centroid and point spread function.

Quote
Day 1559 the light curve in the paper is suddenly cut by half of a percent, when it reaches its highest level and during an otherwise calm period. Apparently some kind of recalibration. It makes me wonder about the 100 year and 4 year dimmings, how well calibrated they are. If one suddenly shifts the entire light curve by half of a percent every other year one might make up any kind of funny correlations. Or maybe there's no data because the curve looks flat before that drop? There are a couple of longer periods with flat curves, is there no data about potential dips there too? Like around day 805 just after the first clean big one.

The processing of the curve (PDCSAP pipeline) is intended for transit detection and produces artefacts like that as a natural consequence of the processing - essentially the algorithm corrects for pointing errors and removes a moving-median from the curve (it is much more complex, but that is the essence), then normalises the values to "1".

When looking at absolute flux, this curve (though easily accessible) is NOT reliable, and you need to calibrate against the full frame images (and other stuff).

Quote
What about the upside here? After day 1528 the star is up to almost 1% brighter than the normalized average. And not in any transiting manner. What could brighten a huge F-star like that by half of a percent steadily for two weeks? Or is the normalization off?

As above, this is a direct consequence of the correction pipeline and is not real (think how a moving median removal behave when there is a massive prolonged dip).

As hop suggested, if you are serious, you need to learn how the instrument actually works and how it can fail.

--- Tony

Also this has been explained to the OP at various times to no avail.
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 04/02/2017 03:53 PM
So regarding the obvious lack of a steady repetition of the dips. Does it suggest (as seems the implication to me), that whatever is orbiting the star is speeding up, slowing down, and/or changing orbits between one orbit and the next?

And also,  is the star "lifting" hypothesis as presented by one theorist a few months ago still a potential solution, given the data as it stands?
Title: Re: Boyajians Star Updates And Discussion
Post by: TakeOff on 04/02/2017 05:30 PM
The space craft rotated 90 degrees every quarter, such that each target star is on a different CCD module, in a different orientation. Which means not only that different pixels are collected, but the optimal aperture for wach quarter is different as well. So any fault would have to affect *only* the pixels in the optimal aperture on 4 different CCDs and not affect any adjacent pixels.
There are other possible failure modes. Without any astrophysical explanation or independent observation, a technical malfunction must be the base case conclusion. Both big anomalies occurred just after the telescope was rotated, and rotated to the same orientation. But then the anomalies continue after it is turned again, so it's not about failing elements in the CCD, but other things can fail when the spacecraft is rotated.
Quote
Quote
What confidence intervals should one have in mind when looking at the light curve in Boyajian's paper? How good is the time resolution of the dips, could it be that they went down to zero for a few seconds?

No. The CCD pixels collect flux for 30 minutes (in long cadence). Then an overall flux value is created from a set of aperture pixels selected from the current pixel centroid and point spread function.
So the bottom flux of the light curve is unconstrained? Could it bottom out on  -100%?
Does the light curve really bounce from crashing to soaring within a 30 second period? From a star of about 2 million kilometer diameter.

Quote
What about the upside here? After day 1528 the star is up to almost 1% brighter than the normalized average. And not in any transiting manner. What could brighten a huge F-star like that by half of a percent steadily for two weeks? Or is the normalization off?

Quote
As above, this is a direct consequence of the correction pipeline and is not real (think how a moving median removal behave when there is a massive prolonged dip).

As hop suggested, if you are serious, you need to learn how the instrument actually works and how it can fail.

--- Tony

So, does the normalization uncertainty explain the brightening of about 1% above the normalized level, is it not considered to be astrophysical?
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 04/02/2017 08:41 PM
So the bottom flux of the light curve is unconstrained? Could it bottom out on  -100%?
Does the light curve really bounce from crashing to soaring within a 30 second period? From a star of about 2 million kilometer diameter.
Detailed descriptions of the pipeline and data products are available from https://keplergo.arc.nasa.gov/

However, it's important to remember that the output of the standard pipeline is not the only thing anyone has looked at. Instrumental error or pipeline artifacts was the most obvious candidate when this thing was initially discovered, and the original group looked at the data at various levels to rule that out. Others have subsequently re-analyzed the data in various ways.
Title: Re: Boyajians Star Updates And Discussion
Post by: notsorandom on 04/03/2017 02:18 PM
So regarding the obvious lack of a steady repetition of the dips. Does it suggest (as seems the implication to me), that whatever is orbiting the star is speeding up, slowing down, and/or changing orbits between one orbit and the next?

And also,  is the star "lifting" hypothesis as presented by one theorist a few months ago still a potential solution, given the data as it stands?
Whatever blocked the light doesn't have to be in orbit of the star. It could be something like a gas or dust cloud in the interstellar medium. It could also be a comet swarm or something similar passing through the system or having been knocked onto a hyperbolic trajectory from the far reaches of the system by a passing star. It also doesn't have to be one single thing. A swarm of objects all in different orbits would make a pattern of dips that would look random until observed long enough to detect a pattern.
Title: Re: Boyajians Star Updates And Discussion
Post by: TakeOff on 04/03/2017 02:39 PM
So regarding the obvious lack of a steady repetition of the dips. Does it suggest (as seems the implication to me), that whatever is orbiting the star is speeding up, slowing down, and/or changing orbits between one orbit and the next?

And also,  is the star "lifting" hypothesis as presented by one theorist a few months ago still a potential solution, given the data as it stands?
Whatever blocked the light doesn't have to be in orbit of the star. It could be something like a gas or dust cloud in the interstellar medium. It could also be a comet swarm or something similar passing through the system or having been knocked onto a hyperbolic trajectory from the far reaches of the system by a passing star. It also doesn't have to be one single thing. A swarm of objects all in different orbits would make a pattern of dips that would look random until observed long enough to detect a pattern.
Two Earth years apart explaining both the single very clean asymmetrical first deep dip, and then two years later also explain the pretty chaotic light curve including a couple of deep asymmetric dips too? Somehow anything passed between us and it, but never between us and any other star (as in 160,000 stars in the same telescope), in order to cause this light curve? Who can blame me for not buying that. I might've bought one of them, but not both.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 04/03/2017 02:48 PM
It's clear this needs posting on here again from Jason Wright.

http://sites.psu.edu/astrowright/2016/08/30/what-could-be-going-on-with-boyajians-star-part-i/
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 04/03/2017 04:04 PM
So regarding the obvious lack of a steady repetition of the dips. Does it suggest (as seems the implication to me), that whatever is orbiting the star is speeding up, slowing down, and/or changing orbits between one orbit and the next?

And also,  is the star "lifting" hypothesis as presented by one theorist a few months ago still a potential solution, given the data as it stands?
Whatever blocked the light doesn't have to be in orbit of the star. It could be something like a gas or dust cloud in the interstellar medium. It could also be a comet swarm or something similar passing through the system or having been knocked onto a hyperbolic trajectory from the far reaches of the system by a passing star. It also doesn't have to be one single thing. A swarm of objects all in different orbits would make a pattern of dips that would look random until observed long enough to detect a pattern.
Two Earth years apart explaining both the single very clean asymmetrical first deep dip, and then two years later also explain the pretty chaotic light curve including a couple of deep asymmetric dips too? Somehow anything passed between us and it, but never between us and any other star (as in 160,000 stars in the same telescope), in order to cause this light curve? Who can blame me for not buying that. I might've bought one of them, but not both.

Isn't it just as hard to explain why this purported observational error happens (many times, even!) only with this particular star?
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 04/03/2017 04:16 PM
Isn't it just as hard to explain why this purported observational error happens (many times, even!) only with this particular star?

Harder!

This supposed error only affects pixels in the optimal aperture for the star, and only when those pixels are observing that star (one quarter a year) ... and the pixels are on 4 different CCDs in different orientations, and the aperture is a different shapes in each of the different quarters. Read-out errors are precluded due to this as well ... very much special pleading.

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 04/03/2017 04:59 PM
Isn't it just as hard to explain why this purported observational error happens (many times, even!) only with this particular star?

Harder!

This supposed error only affects pixels in the optimal aperture for the star, and only when those pixels are observing that star (one quarter a year) ... and the pixels are on 4 different CCDs in different orientations, and the aperture is a different shapes in each of the different quarters. Read-out errors are precluded due to this as well ... very much special pleading.

--- Tony

So it's aliens. Not building a Dyson sphere around the star, but instead they're messing up with Kepler.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 04/19/2017 07:36 AM
Have Aliens Built Huge Structures around Boyajian's Star?

https://www.scientificamerican.com/article/have-aliens-built-huge-structures-around-boyajian-rsquo-s-star/

Unfortunately it's behind a paywall for now.
Title: Re: Boyajians Star Updates And Discussion
Post by: ChrisWilson68 on 04/19/2017 08:15 AM
I think we should split this thread into two separate threads.

Thread A: For the one poster who thinks it's an observational error to argue with everyone else.

Thread B: For all other discussions of Boyajian's Star exception debating whether it's likely to be observational error.

I think the vast majority of people here are more interested in B than A and it's unfortunate all those people have to wade through so many posts that belong in thread A.
Title: Re: Boyajians Star Updates And Discussion
Post by: baldusi on 04/19/2017 12:26 PM
I think we should split this thread into two separate threads.

Thread A: For the one poster who thinks it's an observational error to argue with everyone else.

Thread B: For all other discussions of Boyajian's Star exception debating whether it's likely to be observational error.

I think the vast majority of people here are more interested in B than A and it's unfortunate all those people have to wade through so many posts that belong in thread A.
There's also the "Ignore List" and the "Report to moderator" functionality.
Title: Re: Boyajians Star Updates And Discussion
Post by: LouScheffer on 04/19/2017 02:58 PM
Here's a horribly non-scientific, ad hominum observation that has changed my mind about whether the long term dimming is real.

There is debate over this issue, with Schaefer convinced of long term dimming, and Hippke arguing that it's statistical fluctuations in a difficult-to-calibrate data set.  Recently I had cause for an email exchange with Hippke, on a different topic.  From these I get the impression of a smart, enthusiastic, big picture guy.   But conversely, at least in my interaction, he was not the kind of scientist who obsessively worries about the finest of details.

Extracting the long term dimming, if any, from these difficult data sets, needs extreme attention to detail.  I've never met Schaefer, but the impression I get from his papers is that's right up his alley. 

So before, there were two pieces of evidence for dimming (Schaefer long term, and Montet's dimming during Kepler).  There was one against, which was Hippke.  Classically, science should be only about the evidence, and not about the scientist, but in a true Bayesian analysis all information should be considered (especially since I don't have the time, inclination, or data to do the analysis myself).  My personal guess as to whether the dimming is real has risen from about 2/3 to about 9/10, based upon my new found skepticism of the competing analysis, based only on the apparent personality of the proposer.  Scientifically ugly, but that's the way I feel....
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 04/23/2017 09:13 PM
Should be a new SETI related paper from Jason Wright published Tuesday.

https://mobile.twitter.com/Astro_Wright/status/856208078282178560
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 04/25/2017 07:01 PM
Should be a new SETI related paper from Jason Wright published Tuesday.

https://mobile.twitter.com/Astro_Wright/status/856208078282178560

This is the paper: https://arxiv.org/abs/1704.07263

(Not directly related to Boyajian's star, though)
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 04/25/2017 07:05 PM
Should be a new SETI related paper from Jason Wright published Tuesday.

https://mobile.twitter.com/Astro_Wright/status/856208078282178560

This is the paper: https://arxiv.org/abs/1704.07263

(Not directly related to Boyajian's star, though)

That's a pretty way out there topic for him to be writing a paper on!

Tweeted exchange by him about Doctor Who and the paper.

Quote
Jonathan McDowell‏ @planet4589
Prior technological species. Jason doesn't address Dr Who's Silurians specifically, though.
Jason Wright‏ @Astro_Wright
Replying to @Astro_Wright and @AdamFrank4
(link: https://arxiv.org/abs/1704.07263) arxiv.org/abs/1704.07263

Jason Wright‏ @Astro_Wright

Replying to @planet4589
Only because none of my Whovian tweeps told me about them when I asked for examples! ;-)
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 04/26/2017 11:49 AM
Atlantic article on the above paper.

https://www.theatlantic.com/science/archive/2017/04/was-there-anybody-out-there/524235/
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 04/29/2017 03:36 PM
As much as the idea appeals to me I find it difficult to see how evidence of prior spacefaring civilizations would not be visible in orbit or on moons etc. How long will the US flag on the moon survive? Now imagine entire bases on bodies where almost no erosion occurs.

Not to mention artifacts in  orbital space, where preservation is effectively for ever. If a satellite was in geostationary orbit around Venus or Mars, how long would it remain in place? Forever? Or are there mechanisms that will inevitably disturb it?
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 04/29/2017 04:47 PM
As much as the idea appeals to me I find it difficult to see how evidence of prior spacefaring civilizations would not be visible in orbit or on moons etc. How long will the US flag on the moon survive? Now imagine entire bases on bodies where almost no erosion occurs.

Not to mention artifacts in  orbital space, where preservation is effectively for ever. If a satellite was in geostationary orbit around Venus or Mars, how long would it remain in place? Forever? Or are there mechanisms that will inevitably disturb it?

Nothing lasts forever. Even our satellites in geostationary orbit will I believe after a million years return to Earth and he's talking about far longer time scales than that.
Title: Re: Boyajians Star Updates And Discussion
Post by: ChrisWilson68 on 04/29/2017 04:59 PM
As much as the idea appeals to me I find it difficult to see how evidence of prior spacefaring civilizations would not be visible in orbit or on moons etc. How long will the US flag on the moon survive? Now imagine entire bases on bodies where almost no erosion occurs.

Not to mention artifacts in  orbital space, where preservation is effectively for ever. If a satellite was in geostationary orbit around Venus or Mars, how long would it remain in place? Forever? Or are there mechanisms that will inevitably disturb it?

I agree.  It seems like there's a lot of evidence against the idea.

A civilization that had expanded throughout the solar system would have been likely to leave noticeable sites on bodies throughout the system, including our moon and other airless bodies without any erosion processes to destroy the evidence, and we should have found it by now.

The only fix I can think of for that is to assume the earlier civilization decided to leave and return our system to a natural state, removing all clear evidence of its existence.  Think of places where we've removed our structures to restore wetlands or other natural habitats.

But then there's still the problem of where the civilization arose.  We arose from a long line of complex organisms that left a rich fossil legacy over hundreds of millions of years.  It's not really plausible that a civilization arose a billion years ago without coming from hundreds of millions of years of complex organisms and there is no record at all that we've found of that.  Are we to believe that they dug up every fossil everywhere on the Earth no matter how deep for a 500 million year period?

They could have arisen from some species in the fossil record after the Cambrian explosion, but then they're relatively recent and it would be hard for them to erase every artifact they ever left.  Imagine trying to find every pot shard and every arrowhead our ancestors left throughout the planet to erase the record of our existence.  And why?  When we restore a natural environment, it's so that natural systems can go back to work, not to try to erase evidence for future archaeologists.

If they didn't arise on Earth but they were indigenous to our Solar System, where did they arise?  If they arose on Mars, we would expect that they arose from hundreds of millions of years of ancestors that left a fossil record, and we've poked around on Mars enough that we would expect to have noticed some of that fossil record by now.  Most other bodies aren't really conducive to evolution of a large, complex life form, except the Earth, Mars, and Venus.

So, Venus seems like the only possibility left.  Maybe Venus was once more friendly to life and it arose, built a civilization, expanded to the solar system, then restored the system to a mostly natural state and left.  It seems unlikely, but not entirely impossible.
Title: Re: Boyajians Star Updates And Discussion
Post by: ChrisWilson68 on 04/29/2017 05:02 PM
As much as the idea appeals to me I find it difficult to see how evidence of prior spacefaring civilizations would not be visible in orbit or on moons etc. How long will the US flag on the moon survive? Now imagine entire bases on bodies where almost no erosion occurs.

Not to mention artifacts in  orbital space, where preservation is effectively for ever. If a satellite was in geostationary orbit around Venus or Mars, how long would it remain in place? Forever? Or are there mechanisms that will inevitably disturb it?

Nothing lasts forever. Even our satellites in geostationary orbit will I believe after a million years return to Earth and he's talking about far longer time scales than that.

But M.E.T. has a point about landing sites on our Moon and similar bodies.  They would be expected to preserve visible evidence for billions of years, unless they happen to be hit by impactors.  If there were multiple landing sites on the Moon, it's unlikely all were destroyed by impacts.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 04/29/2017 05:05 PM
As much as the idea appeals to me I find it difficult to see how evidence of prior spacefaring civilizations would not be visible in orbit or on moons etc. How long will the US flag on the moon survive? Now imagine entire bases on bodies where almost no erosion occurs.

Not to mention artifacts in  orbital space, where preservation is effectively for ever. If a satellite was in geostationary orbit around Venus or Mars, how long would it remain in place? Forever? Or are there mechanisms that will inevitably disturb it?

Nothing lasts forever. Even our satellites in geostationary orbit will I believe after a million years return to Earth and he's talking about far longer time scales than that.

But M.E.T. has a point about landing sites on our Moon and similar bodies.  They would be expected to preserve visible evidence for billions of years, unless they happen to be hit by impactors.  If there were multiple landing sites on the Moon, it's unlikely all were destroyed by impacts.

Just because some natural features on certain bodies can last a long time does not automatically equate to the same being true of complex artificial structures.
Title: Re: Boyajians Star Updates And Discussion
Post by: ChrisWilson68 on 04/29/2017 05:53 PM
As much as the idea appeals to me I find it difficult to see how evidence of prior spacefaring civilizations would not be visible in orbit or on moons etc. How long will the US flag on the moon survive? Now imagine entire bases on bodies where almost no erosion occurs.

Not to mention artifacts in  orbital space, where preservation is effectively for ever. If a satellite was in geostationary orbit around Venus or Mars, how long would it remain in place? Forever? Or are there mechanisms that will inevitably disturb it?

Nothing lasts forever. Even our satellites in geostationary orbit will I believe after a million years return to Earth and he's talking about far longer time scales than that.

But M.E.T. has a point about landing sites on our Moon and similar bodies.  They would be expected to preserve visible evidence for billions of years, unless they happen to be hit by impactors.  If there were multiple landing sites on the Moon, it's unlikely all were destroyed by impacts.

Just because some natural features on certain bodies can last a long time does not automatically equate to the same being true of complex artificial structures.

If the Apollo landings had happened 3 billion years ago, I believe that we would have noticed them with our mapping of the lunar surface.  I see no credible mechanism for their deterioration in a way that would make them not be apparent 3 billion years later, unless they all happened to be hit by large impacts.

None of the mechanisms that would corrode or erode them on Earth apply on the Moon, and the mechanisms that could degrade them on the Moon would not destroy gross features.
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 04/29/2017 07:47 PM
If the Apollo landings had happened 3 billion years ago, I believe that we would have noticed them with our mapping of the lunar surface.  I see no credible mechanism for their deterioration in a way that would make them not be apparent 3 billion years later, unless they all happened to be hit by large impacts.

I'd think that in 3 billion years a large impact nearby would be rather likely to have happened. 3 billion years also a very long time for erosion due to micrometeorite impacts to take place.
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 04/29/2017 09:10 PM
As much as the idea appeals to me I find it difficult to see how evidence of prior spacefaring civilizations would not be visible in orbit or on moons etc. How long will the US flag on the moon survive? Now imagine entire bases on bodies where almost no erosion occurs.

Not to mention artifacts in  orbital space, where preservation is effectively for ever. If a satellite was in geostationary orbit around Venus or Mars, how long would it remain in place? Forever? Or are there mechanisms that will inevitably disturb it?

I agree.  It seems like there's a lot of evidence against the idea.

A civilization that had expanded throughout the solar system would have been likely to leave noticeable sites on bodies throughout the system, including our moon and other airless bodies without any erosion processes to destroy the evidence, and we should have found it by now.

The only fix I can think of for that is to assume the earlier civilization decided to leave and return our system to a natural state, removing all clear evidence of its existence.  Think of places where we've removed our structures to restore wetlands or other natural habitats.

But then there's still the problem of where the civilization arose.  We arose from a long line of complex organisms that left a rich fossil legacy over hundreds of millions of years.  It's not really plausible that a civilization arose a billion years ago without coming from hundreds of millions of years of complex organisms and there is no record at all that we've found of that.  Are we to believe that they dug up every fossil everywhere on the Earth no matter how deep for a 500 million year period?

They could have arisen from some species in the fossil record after the Cambrian explosion, but then they're relatively recent and it would be hard for them to erase every artifact they ever left.  Imagine trying to find every pot shard and every arrowhead our ancestors left throughout the planet to erase the record of our existence.  And why?  When we restore a natural environment, it's so that natural systems can go back to work, not to try to erase evidence for future archaeologists.

If they didn't arise on Earth but they were indigenous to our Solar System, where did they arise?  If they arose on Mars, we would expect that they arose from hundreds of millions of years of ancestors that left a fossil record, and we've poked around on Mars enough that we would expect to have noticed some of that fossil record by now.  Most other bodies aren't really conducive to evolution of a large, complex life form, except the Earth, Mars, and Venus.

So, Venus seems like the only possibility left.  Maybe Venus was once more friendly to life and it arose, built a civilization, expanded to the solar system, then restored the system to a mostly natural state and left.  It seems unlikely, but not entirely impossible.

I agree that Venus is perhaps the most likely candidate where entire cities could have existed say a billion years ago, before being wiped out - perhaps by one of those cataclysmic resurfacing events that was theorized at one stage to have periodically covered the entire surface of Venus in magma. I don't know if that theory still holds, but I think we know little enough about Venus to make the idea of lost civilizations at least plausible.

But it is evidence in space that seems more difficult to get rid off. Unless the civilization was only at the beginning of its space exploration era, perhaps comparable to where we are today. Then evidence could perhaps have vanished, over billions of years. But if they spread throughout the solar system, maybe 500 years further advanced than we are today before being wiped out, well, then I find it difficult to imagine that all such solar system evidence would have vanished.
Title: Re: Boyajians Star Updates And Discussion
Post by: ChrisWilson68 on 04/29/2017 09:15 PM
If the Apollo landings had happened 3 billion years ago, I believe that we would have noticed them with our mapping of the lunar surface.  I see no credible mechanism for their deterioration in a way that would make them not be apparent 3 billion years later, unless they all happened to be hit by large impacts.

I'd think that in 3 billion years a large impact nearby would be rather likely to have happened. 3 billion years also a very long time for erosion due to micrometeorite impacts to take place.

I don't think so.  The vast majority of the surface of the moon is more than 3 billion years old.  Most craters you see today came from the Late Heavy Bombardment that came in the closing stages of the formation of the solar system around 3.8 billion years ago.  And even with all the craters from the LHB, the majority of the surface of the moon is not craters, it's just marked with craters, with non-crater areas between the craters.

Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 04/29/2017 11:42 PM
Folks, this stuff about artifacts in the solar system is far OT from "Boyajians Star Updates And Discussion" I'd suggest a split starting at http://forum.nasaspaceflight.com/index.php?topic=41704.msg1670474#msg1670474

Most craters you see today came from the Late Heavy Bombardment that came in the closing stages of the formation of the solar system around 3.8 billion years ago.
No, most large impact craters date from billions of years ago. Even the youngest areas of the moon are heavily impact gardened once you get down to 10s of meter scales relevant to preserving something like Apollo sites.
Title: Re: Boyajians Star Updates And Discussion
Post by: ChrisWilson68 on 04/29/2017 11:51 PM
Folks, this stuff about artifacts in the solar system is far OT from "Boyajians Star Updates And Discussion" I'd suggest a split starting at http://forum.nasaspaceflight.com/index.php?topic=41704.msg1670474#msg1670474

Quote
Most craters you see today came from the Late Heavy Bombardment that came in the closing stages of the formation of the solar system around 3.8 billion years ago.
No, most large impact craters date from billions of years ago. Even the youngest areas of the moon are heavily impact gardened once you get down to 10s of meter scales relevant to preserving something like Apollo sites.

Based on what evidence are you claiming this?
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 04/30/2017 04:11 AM
Based on what evidence are you claiming this?
I'm tempted to just go full Jim here, because this is really basic planetary science 101 stuff.... but LRO for example provides direct evidence of the current cratering rate
http://www.nature.com/nature/journal/v538/n7624/full/nature19829.html

Quote
We also observe a secondary cratering process that we estimate churns the top two centimetres of regolith on a timescale of 81,000 years—more than a hundred times faster than previous models estimated from meteoritic impacts (ten million years)

Note even if the old estimate were correct, you are still off by many orders of magnitude.

The timescale to erase the Apollo hardware may be significantly longer than turning over 2cm of regolith, but it's not going to be gigayears.
Quote
And even with all the craters from the LHB, the majority of the surface of the moon is not craters, it's just marked with craters, with non-crater areas between the craters.
The above also shows this is totally incorrect. At meter scales, the surface is basically saturated. All that rolling busted up regolith you see in LROC and surface mission images is craters and ejecta on craters until it all fades into a jumbled mess.
Title: Re: Boyajians Star Updates And Discussion
Post by: Phil Stooke on 04/30/2017 04:31 AM
Hop is quite right about this.  When you look at an LRO NAC image of small craters in an area a few km across, none of them are 3 Gy old.  Imagine a fresh lava flow just emplaced on the Moon.  100 My later it is covered with small craters (say 1 to 10 m across in this area a few km across), and a thin layer of mingled ejecta, a thin regolith.  100 My after that it looks the same, but it's a whole new population of small craters and a thicker regolith.  100 My later it's another whole set of new craters and the regolith is getting thicker again.  Apollo hardware may last a few millions or even tens of millions of years, but it's getting pretty beaten up by then, not to mention spattered with ejecta on and off.  It is not going to last billions of years, that is a common misconception because supposedly 'there is no erosion on the Moon'.  Not true, of course, the lunar surface is constantly being sandblasted by small stuff.  There is a big literature on impact gardening, but as Hop says the new studies speed up the process considerably.  My credentials? I teach planetary image interpretation.

Oops, I guess we are a bit off topic!
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 04/30/2017 05:50 AM
Still about erosion rate on the Moon: from http://onlinelibrary.wiley.com/doi/10.1002/2014JE004698/pdf
Quote
Abstract
Landscape evolution on the Moon is dominated by impact cratering in the post-maria period.
In this study, we mapped 800 m to 5 km diameter craters on 30% of the lunar maria and extracted their
topographic profiles from digital terrain models created using the Kaguya Terrain Camera. We then
characterized the degradation of these craters using a topographic diffusion model. Because craters have a
well-understood initial morphometry, these data provide insight into erosion on the Moon and the topographic
diffusivity of the lunar surface as a function of time. The average diffusivity we calculate over the past 3 Ga is
~5.5 m2/Myr. With this diffusivity, after 3 Ga, a 1 km diameter crater is reduced to approximately ~52% of its
initial depth and a 300 m diameter crater is reduced to only ~7% of its initial depth, and craters smaller than
~200–300 m are degraded beyond recognition. Our results also allow estimation of the age of individual
craters on the basis of their degradation state, provide a constraint on the age of mare units, and enable
modeling of how lunar terrain evolves as a function of its topography.
Title: Re: Boyajians Star Updates And Discussion
Post by: LouScheffer on 04/30/2017 05:57 AM

Not to mention artifacts in  orbital space, where preservation is effectively for ever. If a satellite was in geostationary orbit around Venus or Mars, how long would it remain in place? Forever? Or are there mechanisms that will inevitably disturb it?
How about the stuff in heliocentric orbits?   We find 10 meter sized asteroids all the time, presumably billions of years old.  So presumably spacecraft in such orbits could be there for quite a while.  We've even detected suspicious looking objects in such orbits, but projecting back they all seem to intersect the vicinity of the Earth after the beginning of the space age.  So likely they are space junk from our own civilization.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 04/30/2017 07:38 AM
Anyway it's verging on the ludicrous to think we can predict what's going to happen to the solar system in the next billion years. Any of a hundred things could happen from a passing star disturbing the Oort cloud causing another bombardment of the inner solar system to a rogue planet or black hole passing through it causing all sorts of disruption. It's impossible to say. I believe on that timescale it's calculated that at some point much sooner than that Mercury's orbit is likely to mean it will clip either Venus or even the Earth. Any of these events could wipe out much evidence that we even existed.
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 04/30/2017 07:14 PM
How about the stuff in heliocentric orbits?   We find 10 meter sized asteroids all the time, presumably billions of years old.
The ~10 meter sized asteroids we see are almost certainly not billions of years old. NEAs generally have dynamical lifetimes of a few to perhaps tens of millions of years, and very small asteroids may have even shorter lives for other reasons. The generally accepted picture is that small asteroids are generated in collisions in the main belt, Yarkovsky drifts them into unfavorable resonances with Jupiter, after which they are quickly ejected or smash into something.

The impact rate on small bodies in near earth orbits is also not terribly far off to what the surface of the moon experiences. AFAIK the gravitational enhancement for Earth is only a factor a few, and the Moon is far less.

The outer solar system would be a lot better for long term parking, but anything out there would be a lot harder to detect.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/01/2017 07:17 PM
Yet another explanation to explain the odd behaviour of this star.

Is Tabby’s Star Really a Planet Eater?

http://trendintech.com/2017/05/01/is-tabbys-star-really-a-planet-eater/
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/02/2017 09:24 PM
April 25, 2017
|
Tabby Boyajian
Hello all,
 
It is a pleasure to announce that as of April 1, 2017, we are now taking photometric data of KIC 8462852 with the LCO 0.4m network thanks to the funds raised by YOU via Kickstarter! We are now paid in full for monitoring our star until June 1, 2018. But that is not all: we still have a couple lose ends to tie up for the project's reimbursements, and I estimate that the remaining funds will cover telescope time until November 30, 2018. What an amazing success!
 
Data are streaming in and we continue to refine our pipeline to improve on the quality and automated routines to identify the next dip. As mentioned in the last report, a sensitive time for us to watch began and the end of February 2017, where an object with a 727 day orbital period would have passed in front of the star and made a drop in light. The 727 days corresponded to the time interval between the two largest dips in the Kepler data at day 792 (18%) and day 1519 (22%). These dips look nothing alike each other, but the idea is that the occulter could be changing shape (for whatever reason) throughout its orbit. Alas, no dip was recovered during this time. However, if we take the same argument and relax the time the second dip occurred, the "sensitive" window remains open for a few more months. We may relax the time the second dip (at day 1519) occurs because it was not alone - it came in a huge complex of dips spanning almost 100 days, where any of these objects could possibly re-enter our line of sight and produce another dip. Another issue with the proposed 727 day orbital period (big dip to big dip) was that we should have seen an additional big dip around day 65 of the Kepler dataset, and we did not (this assumes the 727 day orbital period, and projecting it back in time from the 18% dip that occurred at day 792). Finally, an analysis of historic records reveal a putative dip that occurred October 24 1978, which also fails to match any regularity in the timing of when dips occur.
 
I know what you are thinking - these aren't great guesses to what and when things might happen. But remember, if we could predict anything that the star would be doing, we wouldn't have to be monitoring it like we are now. Knowing when it is and when it is not dipping are important to figuring out what is happening. And from what we have learned of the star so far, it doesn't do what we expect it to do.
 
Another item worth noting is that we just submitted a proposal to look at the star with the Hubble Space Telescope. This is motivated by the fundamental question of where in space (circumstellar or interstellar) the occulting bodies lie. We plan to study this by observing the star in the ultraviolet along with a control star in the same volume of space. The ultraviolet is by far the most sensitive region for assessing absorption along the line of sight, both in terms of individual (gas) absorbers and broad-wavelength (dusty) extinction. We wont learn of the proposal's success (or failure) until sometime this summer after the panel meets for peer review. Hubble time is very competitive (typically a 10-1 shot of acceptance) so fingers crossed!

http://www.wherestheflux.com/single-post/2017/04/25/Your-contributions----observations
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 05/03/2017 05:10 AM
Interesting blog post from Tabitha Boyajian.   The LCO scope and SBIG STL-6303 camera and filter set are probably up to the task of measuring the overall light curve, as well as measuring if the dimming is achromatic. 

More interesting is what the proposal for Hubble time contained.  The notion of examining the volume of space around the star seems tailored to the ISM theories.    What exact observations should they propose for Hubble?

Long duration exposures?  How long of an exposure will be needed to bring out much fainter nearby stars, as well as potentially "see" where patches of ISM may be blocking the field of view?

1.  What would they look for with the COS, NICMOS, or ACS instruments?
2.  What theories can be constrained with specific Hubble observations?
3.  What observations can provide support for predictions made by various theories?
4.  What observations can be eliminate certain theories?

Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/15/2017 07:39 PM
Quote
Are the Dyson rings around pulsars detectable?

Z. Osmanov
(Submitted on 11 May 2017 (v1), last revised 12 May 2017 (this version, v2))
In the previous paper (Osmanov 2016) (henceforth Paper-I) we have extended the idea of Freeman Dyson and have shown that a supercivilization has to use ring-like megastructures around pulsars instead of a spherical shell. In this work we reexamine the same problem in the observational context and we show that facilities of modern IR telescopes (VLTI and WISE) might efficiently monitor the nearby zone of the solar system and search for the IR Dyson-rings up to distances of the order of 0.2kpc, corresponding to the current highest achievable angular resolution, 0.001mas. In this case the total number of pulsars in the observationally reachable area is about 64±21. We show that pulsars from the distance of the order of ∼1kpc are still visible for WISE as point-like sources but in order to confirm that the object is the neutron star, one has to use the UV telescopes, which at this moment cannot provide enough sensitivity.

https://arxiv.org/abs/1705.04142
Title: Re: Boyajians Star Updates And Discussion
Post by: TakeOff on 05/16/2017 06:01 AM
Why isn't a back yard commercial consumer telescope enough to detect another 20% dip in the light curve of that star? Hasn't it been something which hundreds of part time astronomers have been looking for constantly since the anomaly was announced, without finding anything to corroborate it?


I don't see how Kepler's anomaly motivates any redirection of any major telescopes or observation efforts.
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 05/16/2017 06:25 AM
Why isn't a back yard commercial consumer telescope enough to detect another 20% dip in the light curve of that star? Hasn't it been something which hundreds of part time astronomers have been looking for constantly since the anomaly was announced, without finding anything to corroborate it?


I don't see how Kepler's anomaly motivates any redirection of any major telescopes or observation efforts.

Major telescopes will be motivated to observe the star if another dip is detected.  Until then, the merits of any telescope time will be weighed on what the observation can measure that is interesting.   That may be the ISM or something else.  It's not up to you or I to judge, so we will see what happens. 
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 05/17/2017 05:29 PM
BBC has a nice roundup on Boyajian's star http://www.bbc.com/earth/story/20170512-the-most-mysterious-star-in-the-galaxy

Nothing really new for people who have been following the story closely, but good quotes from some of the main players. It also touches on the question of why there is interest in continued observation:

Quote
In the past, the discovery of one bizarre object has often heralded a new class of phenomena. So, if history is any indication, Boyajian's Star may be just the beginning.
Title: Re: Boyajians Star Updates And Discussion
Post by: TakeOff on 05/18/2017 01:09 AM
BBC has a nice roundup on Boyajian's star http://www.bbc.com/earth/story/20170512-the-most-mysterious-star-in-the-galaxy (http://www.bbc.com/earth/story/20170512-the-most-mysterious-star-in-the-galaxy)

Nothing really new for people who have been following the story closely, but good quotes from some of the main players. It also touches on the question of why there is interest in continued observation:

Quote
In the past, the discovery of one bizarre object has often heralded a new class of phenomena. So, if history is any indication, Boyajian's Star may be just the beginning.
Well, it has been observed for years. And there's nothing to report.
And history tells us that one-off freak observations like this are perytons, the result of an observatory observing itself. Lots of wishful thinking going on here. When you see a shooting star, close your eyes and make magic wish. Maybe deliberately greedy media profiteering from unfounded sensationalism plays a role in the hype too.
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 05/18/2017 04:07 AM
Well, it has been observed for years. And there's nothing to report.
The time it has been observed is significantly less that the steady phases between dips in the Kepler light curves, and we have no idea how long it was steady before the first dip.
Quote
And history tells us that one-off freak observations like this are perytons, the result of an observatory observing itself.
This is simply not correct. History is full of "weird" observations that have turned out to be mistakes, and also ones that have turned out to be real phenomena. In the case of perytons, it was suspected quite early that they were of terrestrial origin, and RFI in general was known to be capable of producing similar signals. On the other hand, FRBs are superficially similar but were suspected to be astrophysical and have proven so.

In the case of Boyajian's star, no one has a come up with a remotely credible way for instrumental error to explain the actual data. The long term dimming also provides independent, highly suggestive evidence that there is something weird about the star.

As long as the phenomena is unexplained, it's certainly reasonable not to dismiss instrumental error entirely, but to be more than idle speculation, it would need a specific theory consistent with the actual characteristics of the instrument and the data. No one has come up with one yet.
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 05/19/2017 11:37 AM
Well, things are getting interesting: https://twitter.com/Astro_Wright/status/865528682114203648

Quote
ALERT: @tsboyajian's star is dipping This is not a drill. Astro tweeps on telescopes in the next 48 hours: spectra please!
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/19/2017 12:20 PM
Well, things are getting interesting: https://twitter.com/Astro_Wright/status/865528682114203648

Quote
ALERT: @tsboyajian's star is dipping This is not a drill. Astro tweeps on telescopes in the next 48 hours: spectra please!

Yes, Tabby has also tweeted about this:

https://twitter.com/tsboyajian/status/865530700128075780

2% r' band, still in ingress:
https://twitter.com/tsboyajian/status/865542587087601665

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 05/19/2017 12:55 PM
Yay, finally!
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 05/19/2017 12:57 PM
I'd guess people have ToO programs at several telescopes for this? Or maybe there's some frenetic DDT proposal writing going on.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/19/2017 01:07 PM
I suspect both.  BTW, worth noting that this definitively rules out instrumentation error ...

Edit: definitely both; Tabby is asking about DDT turnaround times for SOPHIA :-)

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/19/2017 01:14 PM
Their was a recent paper on this but it's behind a paywall. Luckily someone on Reddit summed it up.

Quote
Am I understanding correctly then that the 800 dip can be explained as a regular shaped object passing in front of the star, but that the ingress and egress halves look different due to the object picking up speed as it slingshots around the star, and so completing the egress faster than the ingress?

Am I also understanding correctly that the authors calculate the orbital speed to be too slow assuming the object is so close to the star? How did they reach these conclusions? What are the starting assumptions for the supposed transiting object?

You can find complete discussion of the paper here.

https://www.reddit.com/r/KIC8462852/comments/6a9tdc/new_paper_the_hypothetical_orbit_of_kic_8462852b/
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/19/2017 01:15 PM
I'd guess people have ToO programs at several telescopes for this? Or maybe there's some frenetic DDT proposal writing going on.

Tabby appears to have re-tweeted Jason's & her alerts to a number of other observatories.

Here's the list.

https://mobile.twitter.com/tsboyajian/status/865542587087601665/people
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 05/19/2017 01:29 PM
Twitter would go down today of all days. Been trying to contact people to get the message out.

Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/19/2017 01:30 PM
Twitter would go down today of all days. Been trying to contact people to get the message out.

It's the aliens I tell you!
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/19/2017 02:14 PM
New Tweet from Tabby.

Quote
Tabetha Boyajian @tsboyajian

Hey @SOFIAtelescope what is the turn around time for a DDT?  #TabbysStar is acting up right now! @AllPlanets

https://mobile.twitter.com/tsboyajian/status/865554450089353216
Title: Re: Boyajians Star Updates And Discussion
Post by: Orbiter on 05/19/2017 02:23 PM
Wow. Hopefully we can get some more obs soon.

Quote
Tabetha Boyajian @tsboyajian
Replying to @ajebson and 10 others
its 2% in r' band and looks like its the start
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/19/2017 02:28 PM
That's just the leading edge so to speak I imagine of whatever it is as seen from our viewpoint.
Title: Re: Boyajians Star Updates And Discussion
Post by: notsorandom on 05/19/2017 02:32 PM
From a Reddit thread (here) (https://www.reddit.com/r/KIC8462852/comments/4yrxrj/why_is_a_dip_predicted_for_marchapril_of_2017/) Dr. Boyajian explained why there might be a dip in late April 2017:
Quote
The prediction simply comes from the assumption that the two large dips seen in the kepler data are from the same orbiting object (though the dip profiles look nothing alike, it is the best we have to work with). So if dip 1 occurred at Kepler day 792 and the middle of the large complex of dips is day 1540, then the orbital period would be the difference between these: 748 days. Therefore, IF the dips 1 and 2 come from the same orbiting source, then we would expect the 3rd big dip at (1540+748)=2288 days and the 4th to be at (2288+748) = 3036 days. Then add 2454833 to convert "kepler day" to "Barycentric Julian day", we get time for the predicted dip 4 at BJD=2457869. Last step is to use the JD converter to figure out what this means to anyone but a computer :). http://aa.usno.navy.mil/data/docs/JulianDate.php We were not monitor the sky when dip#3 would have occurred in April of 2015, but dip 4 is predicted to be at the end of April, 2017. Again, this all lies on the assumption that the large dips we see are from the same object passing in front of us and the star - and this is not necessarily the case. But for now, this is the best guess. ~Tabby
So we are seeing this dip only a little later than expected! I know three data points do not make a trend and this is not (yet) nearly as large of a dip. However if we are seeing this phenomenon repeat then it almost has to be something in orbit around the star thus ruling out an explanation involving something in interstellar space.
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 05/19/2017 02:49 PM
Aww Tony, you're famous  ;D;

https://arstechnica.com/science/2017/05/tabbys-star-is-dimming-again-and-astronomers-are-excited/
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/19/2017 03:09 PM
SWIFT is now observing.

https://www.swift.psu.edu/operations/obsSchedule.php?t=34113
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/19/2017 04:15 PM
New Tweet by Jason Wright

Quote
Jason Wright @Astro_Wright

Replying to @paulsanderson and @tsboyajian
We are down about 3% in r

https://mobile.twitter.com/Astro_Wright/status/865585360356515840
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/19/2017 04:45 PM
Aww Tony, you're famous  ;D;

https://arstechnica.com/science/2017/05/tabbys-star-is-dimming-again-and-astronomers-are-excited/

LOL, only slightly. My twitter feed has exploded this afternoon :-)

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 05/19/2017 05:10 PM
The great thing is if it weren't for the kickstarter we wouldn't have this opportunity.
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 05/19/2017 05:20 PM
Re: SOFIA
https://twitter.com/wtreach/status/865617413215105024
Quote
With a justified proposal, we could observe #tabbysstar on 5/24/17 with the FPI+ camera. The infrared instrument is EXES on that flight.

Also,
https://twitter.com/brettmor/status/865617742048645120
Quote
I'll be getting a spectrum with the echelle on the APO ARC 3.5 m tonight near sunrise
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/19/2017 05:30 PM
There are others in the pipeline, I think, but not confirmed yet
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/19/2017 05:38 PM
There are others in the pipeline, I think, but not confirmed yet

Can they get time on Hubble, there is DDT after all?
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/19/2017 05:46 PM
Quote
UC Berkeley SETI @BerkeleySETI

Join us in 45 minutes (11am PDT) for a live chat with @Astro_Wright on the latest @tsboyajian Star observations

https://mobile.twitter.com/BerkeleySETI/status/865617660763029504
Title: Re: Boyajians Star Updates And Discussion
Post by: LouScheffer on 05/19/2017 07:08 PM
Kepler simply suffered a malfunction. There's no possible physical explanation between the star and the telescope. The error is between the telescope and us.
This is precisely what Arthur C. Clark called a "failure of imagination", as in " *I* can't imagine a physical explanation, so there cannot be one".   And it also goes against a suggestion from Bertrand Russell:
Quote
When the experts are agreed, the opposite opinion cannot be held to be certain.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/19/2017 07:16 PM
This has just been posted on the relevant Reddit.

Quote
Jason Wright and Breakthrough Listen astronomer Andrew Siemion were on the video. There is some credible talk that this does help establish a periodicity to the dips, which would rule out anything in the ISM. Jason also said that he's not optimistic about getting ALMA on the star because of its very low elevation angle. We should get spectra from several telescopes, including Keck, but Spitzer wil not be on it. Swift can give us UV measurements, but the error bars are relatively large. No mention of Hubble, or did I miss it?

Longer summary here.

https://www.reddit.com/r/KIC8462852/comments/6c546t/live_chat_soon_with_jason_wright_about_the/dhs0mwo/?context=3
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/19/2017 09:00 PM
Quote
Jason Wright @Astro_Wright

Yes please!  Most useful photometry is probably widest coverage (to constrain reddening) combined with good night-to-night precision.
Zachary Vanderbosch @ZachVanderbosch
Replying to @tsboyajian and 9 others
I'm observing with McDonald 2.1m tonight, simultaneous multi-color photometry is possible.  What are the most useful Sloan filters?
9:34 pm · 19 May 2017

https://mobile.twitter.com/Astro_Wright/status/865667061850062848
Title: Re: Boyajians Star Updates And Discussion
Post by: sghill on 05/19/2017 10:17 PM
This has just been posted on the relevant Reddit.

Quote
Jason Wright and Breakthrough Listen astronomer Andrew Siemion were on the video. There is some credible talk that this does help establish a periodicity to the dips, which would rule out anything in the ISM. Jason also said that he's not optimistic about getting ALMA on the star because of its very low elevation angle. We should get spectra from several telescopes, including Keck, but Spitzer wil not be on it. Swift can give us UV measurements, but the error bars are relatively large. No mention of Hubble, or did I miss it?

Longer summary here.

https://www.reddit.com/r/KIC8462852/comments/6c546t/live_chat_soon_with_jason_wright_about_the/dhs0mwo/?context=3

I can't express how cool I think this is. Real time developments in astronomy are amazing events!
Title: Re: Boyajians Star Updates And Discussion
Post by: jgoldader on 05/19/2017 10:45 PM
There are others in the pipeline, I think, but not confirmed yet

Can they get time on Hubble, there is DDT after all?

DD time on HST probably takes a while.  The telescope runs a command load autonomously, it's not real-time, and the command loads are sequenced far in advance.  Interrupting them is a pretty major event, or at least it was when I was at STscI many years back.  I don't know that they could do better than several days, my gut tells me a week or two might be the best turnaround.

But it's high S/N spectroscopy you want here, not imaging, and that's ground-based stuff, and getting a TO (target of opportunity) observation is a lot more straightforward on the ground.  A UV spectrum with HST to look for enhanced interstellar absorption lines might be worth doing, but there are enough optical features to tell you if it's a dust cloud.  This is exciting!
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 05/19/2017 10:47 PM
This is the archived google hangout for those who didn't see it; https://www.youtube.com/watch?v=eYpIGZS8nJc
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 05/20/2017 05:34 AM
But it's high S/N spectroscopy you want here, not imaging, and that's ground-based stuff, and getting a TO (target of opportunity) observation is a lot more straightforward on the ground.  A UV spectrum with HST to look for enhanced interstellar absorption lines might be worth doing, but there are enough optical features to tell you if it's a dust cloud.
FWIW, they did submit an HST proposal for regular time before the dip started: http://forum.nasaspaceflight.com/index.php?topic=41704.msg1673854#msg1673854

Quote
This is exciting!
Isn't it?!
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/20/2017 06:24 AM
But it's high S/N spectroscopy you want here, not imaging, and that's ground-based stuff, and getting a TO (target of opportunity) observation is a lot more straightforward on the ground.  A UV spectrum with HST to look for enhanced interstellar absorption lines might be worth doing, but there are enough optical features to tell you if it's a dust cloud.  This is exciting!

As much spectroscopy as possible :-) particularly as the observations that showed the first hints it was misbehaving detected H-alpha (and weaker Ca II H & K) emissions, which haven't been seen before. [ see link ]

https://angelrls.wordpress.com/2017/05/20/mysterious-tabbys-star-dims-again-observations-needed/

Nice that the Kickstarter has paid off.  And yes, very exciting!

I know we were offered Keck LGS last night by the scheduled observer, but not sure more AO will tell us much. Though I suspect this has morphed into different observations (hints about HIRES from Jason).

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 05/20/2017 07:11 AM
But it's high S/N spectroscopy you want here, not imaging, and that's ground-based stuff, and getting a TO (target of opportunity) observation is a lot more straightforward on the ground.  A UV spectrum with HST to look for enhanced interstellar absorption lines might be worth doing, but there are enough optical features to tell you if it's a dust cloud.  This is exciting!

As much spectroscopy as possible :-) particularly as the observations that showed the first hints it was misbehaving detected H-alpha (and weaker Ca II H & K) emissions, which haven't been seen before. [ see link ]

https://angelrls.wordpress.com/2017/05/20/mysterious-tabbys-star-dims-again-observations-needed/

Nice that the Kickstarter has paid off.  And yes, very exciting!

I know we were offered Keck LGS last night by the scheduled observer, but not sure more AO will tell us much. Though I suspect this has morphed into different observations (hints about HIRES from Jason).

--- Tony

H-alpha emission would seem to point towards something going on with the star itself, not just interstellar of circumstellar material blocking the light. Hard to think what exactly, though...

edit: well, maybe close enough circumstellar matter could also work, though there'd have to be also IR excess.
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 05/20/2017 07:18 AM
And if I've understood correctly the detection was apparently before the major phase of dimming, will be interesting to see if others confirm while the dimming is in progress.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/20/2017 07:25 AM
H-alpha emission would seem to point towards something going on with the star itself, not just interstellar of circumstellar material blocking the light. Hard to think what exactly, though...

I was wondering more about intervening warm gas, and assumed the detections at H-alpha, Ca II H & K were spotted in usual stellar activity measurements from HERMES

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 05/20/2017 07:33 AM
H-alpha emission would seem to point towards something going on with the star itself, not just interstellar of circumstellar material blocking the light. Hard to think what exactly, though...

I was wondering more about intervening warm gas, and assumed the detections at H-alpha, Ca II H & K were spotted in usual stellar activity measurements from HERMES

--- Tony

That kind of activity just seems un-F-type-like behaviour...
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/20/2017 07:34 AM
Is the star being observed for excess UV?
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/20/2017 07:37 AM
A drop in UV is more likely.  SWIFT is observing it, but last I heard the dip is ~3% and the error bars on SWIFT's UV are 1-2% so the dip is not (yet) detectable with any degree of confidence.

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 05/20/2017 07:42 AM
If it is warm dust though it should be deeper in the UV.  The LCOGT measurements were taken in the Red.
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 05/20/2017 07:45 AM
This is all very exciting.

Just to confirm my understanding, how narrow is the "window" of observation that enables us to detect an object transiting a distant star? What I mean is, if you divide the circumference of the star into 360 degrees, how many of those degrees would fall in a direct line of sight with Earth? 1 degree only? More? Less? Meaning, the "object" needs to orbit on a very specific, narrow plane for us to even observe it passing in front of the star.

What I am trying to get at, in a clumsy way, is whether we are only seeing potential objects in a very narrow band around the star. Meaning if you go with the alien megastructure idea, there could be vastly more of these swarms around the star than we are able to observe in our line of sight.

Am I correct in thinking this?
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 05/20/2017 08:57 AM
If it is warm dust though it should be deeper in the UV.

It depends on dust grain size. With larger grains absorption curve could be flat(ish). You'd need more dust mass to get enough absorption with large grains, though.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/20/2017 09:04 AM
If it is warm dust though it should be deeper in the UV.

It depends on dust grain size. With larger grains absorption curve could be flat(ish). You'd need more dust mass to get enough absorption with large grains, though.

Assuming a ~circular orbit and that the ~750 day period is right, then Tdust at ~1.6AU ~= 300K so peak emission around 10um?

On dust size, yes, that's my understanding as well - with large gains absorption would be pretty flat.

We need more data! When do we want it? Now! ;-)

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 05/20/2017 09:05 AM
Yeah, but what i mean is a detection would be possible with SWIFT depending on what is occulting.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/20/2017 09:07 AM
Yes indeed ... SWIFT UVOT will be very useful; as you say, dip caused by dust should be deeper in the UV

Shame SWIFT isn't really designed for this kind of thing

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 05/20/2017 12:56 PM
Some data  :D:

https://twitter.com/brettmor/status/865904269815193600
Quote
First results from my APO spectrum of #BoyajiansStar (two hours ago, at 5/20 10:34UTC): CaII H & K S-ind = 0.23±0.02. cc @tsboyajian
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 05/20/2017 01:03 PM
Some data  :D:

https://twitter.com/brettmor/status/865904269815193600
Quote
First results from my APO spectrum of #BoyajiansStar (two hours ago, at 5/20 10:34UTC): CaII H & K S-ind = 0.23±0.02. cc @tsboyajian

https://twitter.com/brettmor/status/865911844455669760
Quote
No NaI absorption at 5985 Ang. Black curve is tonight's obs., red is PHOENIX model atmosphere. cc @tsboyajian #BoyajiansStar

Can someone interpret that for the less technically savvy among us?
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/20/2017 01:14 PM
The correct link for the Sodium absorption is:

https://twitter.com/brettmor/status/865916465962074113
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 05/20/2017 01:19 PM
Yeah he deleted the previous tweet so i removed it.

ISM sodium lines seem weaker than from previous Keck measurement?
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/20/2017 01:28 PM
Yeah he deleted the previous tweet so i removed it.

ISM sodium lines seem weaker than from previous Keck measurement?

I think that's an artefact of lower spectral resolution (R=31,500, the earlier one was R=47,000) ... looks broadly consistent with the modelled 3 ISM clouds.

He's also done the potassium one now:
https://twitter.com/brettmor/status/865920618578886657

--- Tony

Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/20/2017 01:34 PM
Some familiar bloke in The Verge now.

https://www.theverge.com/2017/5/20/15668130/star-kic-8462852-tabbys-star-alien-megastructures-light-dimming
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 05/20/2017 01:41 PM
Yeah he deleted the previous tweet so i removed it.

ISM sodium lines seem weaker than from previous Keck measurement?

I think that's an artefact of lower spectral resolution (R=31,500, the earlier one was R=47,000) ... looks broadly consistent with the modelled 3 ISM clouds.

Yeah, the lines are so narrow that lower R may not resolve them. The new spectrum also seems to have lower SNR. Even if there had been a change of ~3% in ISM absorption, it would probably be very hard to see from these spectra.
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 05/20/2017 01:48 PM
Can someone interpret that for the less technically savvy among us?

I think it means the ISM theories will fall out of favor because the periodicity is reinforced.   Megastructures will be discounted because the dip is not achromatic.   No IR excess will constrain theories based on the total absorption.   The star lifting crowd will conjure some explanations tying in the H-alpha signature to their pet alien theories,  and scientists will have to seriously scratch their heads to explain how an F class star can behave this way.

Exciting times!   Great job getting the kickstarter on this!  I'll be at the DAS open sky event tonight,  I'll be the one staying late to see Lyra & Tabbys star come up in the eastern sky.  Not expecting anything but an opportunity to ponder it all
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/20/2017 01:50 PM
Yeah, the lines are so narrow that lower R may not resolve them. The new spectrum also seems to have lower SNR. Even if there had been a change of ~3% in ISM absorption, it would probably be very hard to see from these spectra.

Agreed. The folks using HERMES on the Mercator are apparently seeing the same, though they haven't released data yet (R=85000). So hoping they release theirs soon ...

Oh, and diffuse absorption here:
https://twitter.com/brettmor/status/865923232456622080

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/20/2017 01:54 PM
Now coming out of its dip.

Quote
So, observers - there are signs that the weird star found by @tsboyajian and @planethunters is brightening again after its dip.
2:13 pm · 20 May 2017


Quote
chrislintott @chrislintott
Replying to @chrislintott and 2 others
BUT we know from past behaviour that it can brighten & fade rapidly so more observations from amateurs v. welcome


https://mobile.twitter.com/chrislintott/status/865918682475769856

Always keep an eye on Chris's Twitter as he at least reports on amateur observers unlike some who seem to do their best to ignore them.
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 05/20/2017 01:58 PM
Oh, and diffuse absorption here:
--- Tony

Nothing seems to really stand out compared to the comparison star, but I wouldn't really expect to for such a small change in absorption. For detecting subtle changes SNR looks pretty low, but it's of course a very quick-and-dirty reduction.

edit: Has anyone seen info about how deep the dip was at its deepest?
Title: Re: Boyajians Star Updates And Discussion
Post by: Orbiter on 05/20/2017 02:23 PM
AAVSO data also supports that the dip is over. We were pretty unlucky with the timing of this particular dip. Cygnus isn't high in the sky until 3-4am, with sunrise only a few hours later. However, at least we can verify that Kepler wasn't acting up and these dips are real.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/20/2017 02:28 PM
edit: Has anyone seen info about how deep the dip was at its deepest?

Deepest I've heard was 3% ... that was the level when they sent the alert. Data from LCOGT was 2% at a similar time.
Not heard anything really since, but that's not surprising.

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 05/20/2017 02:28 PM
Weren't the previous large dips also preceded by a series of smaller dips?

EDIT

Having just looked at the Wikipedia light curve history for this star, it appears that there were two approximately 1% dips at around days 100 and 250, with the 15% dip happening around day 800.

But there seems to have been an approximately 2% dip a few days before the big 22% dip around day 1500, and perhaps a 3% dip shortly thereafter.  So this could be similar to one of those.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/20/2017 02:35 PM
And H-alpha & H-beta:

https://twitter.com/brettmor/status/865936714686119937
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/20/2017 02:39 PM
Weren't the previous large dips also preceded by a series of smaller dips?

For context, here is the Kepler kurve. This dip is at +3060 if you use the same JD offset

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 05/20/2017 02:43 PM
Weren't the previous large dips also preceded by a series of smaller dips?

For context, here is the Kepler kurve. This dip is at +3060 if you use the same JD offset

--- Tony

Thank you.

Was the star continuously observed after the end of that graph until today? And if so, what does that tell us just from the frequency of dips? That the objects are not in a regular pattern seems clear. Considering that the interstellar medium blockage theory seems to be discredited now, what could possibly cause the big 15% and 20% dips to not recur?

EDIT

In fact, if we discount the two massive dips, and if we are indeed at around day 3060 now, then we could very well now be observing the repeat of the +-3% dip that occured around day 1530, just after the big 22% dip.

So that could perhaps be a regular object orbiting the star, with the larger dips being caused by something else?
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/20/2017 03:34 PM
Quote
John O'Meara @astronomeara

Replying to @brettmor and @tsboyajian
From about 45 minutes ago with @keckobservatory HIRES

https://mobile.twitter.com/astronomeara/status/865950712676601856
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 05/20/2017 04:18 PM
Got a response from Jason re: if the dimming had stopped;

https://twitter.com/Astro_Wright/status/865962813377966080
Quote
Not sure. Tabby is still processing the photometry.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/20/2017 06:23 PM
So after all the star's spectra remained unchanged during the dip.
Title: Re: Boyajians Star Updates And Discussion
Post by: RotoSequence on 05/20/2017 06:27 PM
So after all the star's spectra remained unchanged during the dip.

As far as I know, that's the spectral result that would most strongly suggest that the dimming is caused by a circumstellar solid object.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/20/2017 06:37 PM
So after all the star's spectra remained unchanged during the dip.

As far as I know, that's the spectral result that would most strongly suggest that the dimming is caused by a circumstellar solid object.

Three times the size of Jupiter?
Title: Re: Boyajians Star Updates And Discussion
Post by: RotoSequence on 05/20/2017 06:42 PM
So after all the star's spectra remained unchanged during the dip.

As far as I know, that's the spectral result that would most strongly suggest that the dimming is caused by a circumstellar solid object.

Three times the size of Jupiter?

Indeed - that or three times the disk area. It's why people started entertaining the Megastructure hypothesis in the first place.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/20/2017 06:43 PM
So after all the star's spectra remained unchanged during the dip.

As far as I know, that's the spectral result that would most strongly suggest that the dimming is caused by a circumstellar solid object.

Three times the size of Jupiter?

Indeed; it's why people started entertaining the Megastructure hypothesis in the first place.

Aren't there gas giants many time the size of Jupiter though?
Title: Re: Boyajians Star Updates And Discussion
Post by: RotoSequence on 05/20/2017 06:44 PM
Aren't there gas giants many time the size of Jupiter though?

TrES-4 is the largest known exoplanet at 1.7 Jupiters.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/20/2017 06:46 PM
Aren't there gas giants many time the size of Jupiter though?

TrES-4 is the largest known exoplanet at 1.7 Jupiters.

Brown Dwarf then, aren't they notoriously difficult to detect?
Title: Re: Boyajians Star Updates And Discussion
Post by: RotoSequence on 05/20/2017 06:47 PM
Aren't there gas giants many time the size of Jupiter though?

TrES-4 is the largest known exoplanet at 1.7 Jupiters.

Brown Dwarf then, aren't they notoriously difficult to detect?

Directly yes, but stellar mass companions have been ruled out to a significant distance by radial velocity techniques. The observed dips around KIC 8462852 (https://static1.businessinsider.com/image/562d2484dd08954e388b45eb-1005-691/kic-8462852-light-curve-boyajian.png) aren't shaped like planet (or star) transit curves (https://www.nature.com/article-assets/npg/nature/journal/v494/n7438/images/nature11914-f1.2.jpg), either.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/20/2017 06:54 PM
So after all the star's spectra remained unchanged during the dip.

We don't know that. A few specific lines have been looked at, but we don't know the dimming is achromatic, and small dips like this (2-3%) need careful analysis to spot the differences.

All we've seen so far is quick-look analysis

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Orbiter on 05/20/2017 07:24 PM
We're not at the point where they can rule out interstellar dust. Tabby B's May 2017 prediction of a transit could very well have been a coincidence. Interstellar dust will reveal itself through more dimming at shorter wavelengths (UV, for example). So far, we haven't see any data on that. Additionally, multiple telescopes around the world were used to collect data on the dip. They need to calibrate the data to offset for the differences in those telescopes too. The events yesterday happened at the speed of light for the astronomical community... processing the data could take many days, even weeks.
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 05/20/2017 08:25 PM
Was the star continuously observed after the end of that graph until today?
No. The star wasn't recognized as interesting until significantly after the end of the Kepler prime mission, and arranging and funding regular monitoring took more time after that. It's also not observable by ground based telescopes for some of the year, although there was some monitoring with SWIFT this winter (See http://www.wherestheflux.com/single-post/2017/02/01/Science-update).

Bottom line: Some dips after the end of the Kepler mission could have been missed. Also, we don't know how long the final sequence Kepler saw lasted.
Quote
And if so, what does that tell us just from the frequency of dips? That the objects are not in a regular pattern seems clear.
The recent dip strengthens the case for a quasi-period around 750 days. See Dr Boyajian's 2016 post titled  "What will happen in May of 2017" (!) http://www.wherestheflux.com/single-post/2016/06/09/What-will-happen-in-May-of-2017

What this means is unclear. It's definitely not strictly periodic, but it's pretty suggestive. It could be compatible with the original comet swarm type theories. It certainly seems to disfavor the interstellar medium, but I'm not sure it completely rules it out.
Quote
Considering that the interstellar medium blockage theory seems to be discredited now, what could possibly cause the big 15% and 20% dips to not recur?
Again, the original "comet swarm" type theories can do this. Sometimes you get big outbursts, sometimes you don't. The ~750 day interval could be separation between products of a breakups on previous orbits rather than the period of the parent body itself.

This is a bit unsatisfactory because it doesn't explain the long term dimming, but the more recent "digested planet" theory might be able to account for both.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/20/2017 08:56 PM
Was the star continuously observed after the end of that graph until today?
No. The star wasn't recognized as interesting until significantly after the end of the Kepler prime mission, and arranging and funding regular monitoring took more time after that. It's also not observable by ground based telescopes for some of the year, although there was some monitoring with SWIFT this winter (See http://www.wherestheflux.com/single-post/2017/02/01/Science-update).

Bottom line: Some dips after the end of the Kepler mission could have been missed. Also, we don't know how long the final sequence Kepler saw lasted.
Quote
And if so, what does that tell us just from the frequency of dips? That the objects are not in a regular pattern seems clear.
The recent dip strengthens the case for a quasi-period around 750 days. See Dr Boyajian's 2016 post titled  "What will happen in May of 2017" (!) http://www.wherestheflux.com/single-post/2016/06/09/What-will-happen-in-May-of-2017

What this means is unclear. It's definitely not strictly periodic, but it's pretty suggestive. It could be compatible with the original comet swarm type theories. It certainly seems to disfavor the interstellar medium, but I'm not sure it completely rules it out.
Quote
Considering that the interstellar medium blockage theory seems to be discredited now, what could possibly cause the big 15% and 20% dips to not recur?
Again, the original "comet swarm" type theories can do this. Sometimes you get big outbursts, sometimes you don't. The ~750 day interval could be separation between products of a breakups on previous orbits rather than the period of the parent body itself.

This is a bit unsatisfactory because it doesn't explain the long term dimming, but the more recent "digested planet" theory might be able to account for both.

A lot of people believe this is a stretch as an explanation due to the lack of IR excess. Even a number of originators of the comet theory think it's a kludge. Plus it requires an almost ridiculous number of comets to work.

I am hoping if nothing else this recent dip analysis gets this theory off the table.
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 05/20/2017 11:04 PM
Live Q&A with Boyajian on David Kipping's Cool Worlds channel, Sunday 11:00 AM ET

https://twitter.com/david_kipping/status/866024954671886336
Quote
OK everyone! Special #CoolWorlds livesteam tomorrow (Sunday) at 11am Eastern featuring @tsboyajian for live Q&A! Send us your questions!

https://twitter.com/david_kipping/status/866059873401942016
Quote
Here's the link:
https://www.youtube.com/watch?v=k_-6SEb2QlM

Questions can be posted in advance on announcement video
https://www.youtube.com/watch?v=m-mjDZq7jN4
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/21/2017 06:46 AM
Will we get a really big dip next or another smaller one as the prior history of this star shows clusters of such events.
Title: Re: Boyajians Star Updates And Discussion
Post by: Orbiter on 05/21/2017 01:14 PM
It's still dipping!!

https://twitter.com/Astro_Wright/status/866272570986962944
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/21/2017 02:48 PM
Here's the AAVSO V data ... I've not looked properly yet, but might just be hints of a secular trend
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/21/2017 03:51 PM
Quote
David Kipping @david_kipping

Heres the figure I showed in the livestream summarizing the (public) observations taken so far. Black dashed isn't a fit but old Kepler data

https://mobile.twitter.com/david_kipping/status/866318056947150848

Latest data is shown in the Q&A with Tabby that's just been recorded:

https://www.youtube.com/watch?v=k_-6SEb2QlM&feature=youtu.be
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 05/21/2017 04:01 PM
Tabby just posted the LCO data:

https://twitter.com/tsboyajian/status/866321094256599041
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/21/2017 04:04 PM
Isn't it initially appearing to be a very good fit for the Kepler data?

By the way does anyone know if there's been recent efforts to look for planets in the system, or is it just too far away without a gravitational lensing event?
Title: Re: Boyajians Star Updates And Discussion
Post by: Orbiter on 05/21/2017 04:34 PM
Isn't it initially appearing to be a very good fit for the Kepler data?


It appears to be a perfect match.

Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/21/2017 05:00 PM
Isn't it initially appearing to be a very good fit for the Kepler data?


It appears to be a perfect match.

Would you say that's indicative of anything?
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 05/21/2017 05:11 PM
Isn't it initially appearing to be a very good fit for the Kepler data?


It appears to be a perfect match.

Perfect match with which previous dip?
Title: Re: Boyajians Star Updates And Discussion
Post by: Orbiter on 05/21/2017 05:13 PM
Isn't it initially appearing to be a very good fit for the Kepler data?


It appears to be a perfect match.

Would you say that's indicative of anything?

I can't really definitively say anything as I'm only a 3rd year Physics undergrad, but I can't imagine that it's not. The dips appearing to line up with a previous Kepler event plus the predicted May 2017 event just strikes me as too coincidental to be interstellar dust. I think it could be something orbiting the star with a period of ~750 days. Lack of excess IR is a big problem with that idea still.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/21/2017 05:19 PM
Isn't it initially appearing to be a very good fit for the Kepler data?


It appears to be a perfect match.

Perfect match with which previous dip?

Look at the Tweet from David Kipping I linked to above. And the further discussion here.

https://mobile.twitter.com/Astro_Wright/status/866342539007324168

Keck data.

https://mobile.twitter.com/astronomeara/status/866310803825152001
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/21/2017 06:32 PM
Perfect match with which previous dip?

Looks like the central dip of the complex around d1540

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/21/2017 06:38 PM
Quote
Jason Wright @Astro_Wright

Replying to @jonfr500 and 2 others
Right now we're just trying to organize what we have! But we have high resolution blue spectra, so we should know soon

https://mobile.twitter.com/Astro_Wright/status/866348359199621120
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 05/21/2017 06:42 PM
Perfect match with which previous dip?

Looks like the central dip of the complex around d1540

--- Tony

Thank you. So it's the same one I was suggesting in my earlier post, when I said:

"In fact, if we discount the two massive dips, and if we are indeed at around day 3060 now, then we could very well now be observing the repeat of the +-3% dip that occured around day 1530, just after the big 22% dip"

If this is confirmed, then the obvious question is, what happened to the big dip? How could it just disappear? Could it perhaps have a much longer orbit, in other words, be farther out from the star than the smaller object? If so, it would make the object even bigger, right?
Title: Re: Boyajians Star Updates And Discussion
Post by: Johnnyhinbos on 05/21/2017 07:00 PM
The opposite. If it was far enough away from the star it could be as small as the head of a pin and block 100% of the light (put your thumb up in the night sky and you can "transit" a billion stars with barely any effort...)

But, what if what we're seeing is an interstellar highway, perhaps many light years away from Tabby's star. Close enough to be found only in its "neighborhood" but still far enough away so that it's apparent size is magnified when observed from 1,400 light years away (i.e., earth). Transits therefore not periodic nor consistent in magnitude...

EDIT: It can be called "Hanzl's Interstellar Transit" theory. Thank you and your welcome :-)
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 05/21/2017 07:10 PM
The opposite. If it was far enough away from the star it could be as small as the head of a pin and block 100% of the light (put your thumb up in the night sky and you can "transit" a billion stars with barely any effort...)

But, what if what we're seeing is an interstellar highway, perhaps many light years away from Tabby's star. Close enough to be found only in its "neighborhood" but still far enough away so that it's apparent size is magnified when observed from 1,400 light years away (i.e., earth). Transits therefore not periodic nor consistent in magnitude...

EDIT: It can be called "Hanzl's Interstellar Transit" theory. Thank you and your welcome :-)

I'm trying to wrap my head around what should be a simple concept. So, if Jupiter was in Mercury's orbit, it would block less of the sun's light than if it was in Pluto's orbit?
Title: Re: Boyajians Star Updates And Discussion
Post by: RotoSequence on 05/21/2017 07:12 PM
The opposite. If it was far enough away from the star it could be as small as the head of a pin and block 100% of the light (put your thumb up in the night sky and you can "transit" a billion stars with barely any effort...)

But, what if what we're seeing is an interstellar highway, perhaps many light years away from Tabby's star. Close enough to be found only in its "neighborhood" but still far enough away so that it's apparent size is magnified when observed from 1,400 light years away (i.e., earth). Transits therefore not periodic nor consistent in magnitude...

EDIT: It can be called "Hanzl's Interstellar Transit" theory. Thank you and your welcome :-)

The "thumb in front of your eyes" hypothesis is strongly constrained by how close the intervening object has to be to the observer to not be absolutely gigantic. Periodicity in the Interstellar Medium is exceedingly improbable because it would require a net relative motion that falls precisely between Earth and KIC 8462852.
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 05/21/2017 08:14 PM
The opposite. If it was far enough away from the star it could be as small as the head of a pin and block 100% of the light (put your thumb up in the night sky and you can "transit" a billion stars with barely any effort...)

I'm trying to wrap my head around what should be a simple concept. So, if Jupiter was in Mercury's orbit, it would block less of the sun's light than if it was in Pluto's orbit?
Yes (the amount of photons hitting the planet falls off by the inverse square law after all), but I suspect what you had in mind is how much light would appear to block to an observer, which depends on how far away the observer is.

When we talk about things orbiting other stars, the distance from Earth to the objects is so much larger than the distance between them we can just treat them as being at the same distance. In that case, the amount of light blocked just depends on the actual sizes of the objects. To an observer on Proxima B, Jupiter would produce essentially the same transit depth whether it orbited at the distance of Mercury or Pluto. To an observer on Jupiter, it blocks out ~180 degrees of sky no matter where it is ;)
Title: Re: Boyajians Star Updates And Discussion
Post by: Mongo62 on 05/21/2017 08:17 PM
Medium Resolution Spectroscopy of Boyajian's Star (KIC 8462852) (http://www.astronomerstelegram.org/?read=10406)

Quote
ATel #10405 reports that a several percent dip in the brightness of KIC 8462852 is underway.

We report medium resolution spectroscopy (R=2500) taken with the FRODOSpec fibre fed integral field spectrograph of the 2.0 meter Liverpool Telescope, La Palma obtained on 20th May 2017 starting at 01:20UT. Three 600 second exposures were obtained, giving a total integration time of 1800 seconds. The wavelength range was 5800 - 9400 Angstroms.

The spectrum is compared with a reference spectrum obtained "out of dip" on 4th July 2016 with an identical instrumental setup and exposure time.

In an initial analysis we find no difference between the two spectra apart from in features that are attributable to the expected variable telluric absorption features in the Earth's atmosphere.


Excerpts of the spectra in the region of H-alpha (https://www.dropbox.com/s/u11lv7d5opeo0rr/KIC-halpha.png?dl=0) and the IR Calcium Triplet (https://www.dropbox.com/s/isev1ymggilx4hl/KIC-Ca.png?dl=0) are shown (the different ripples in the two Ca spectra are due to CCD fringing in the detector). Taking the ratio of the two spectra gives standard deviations per pixel of 2 percent of the continuum level in the H-alpha region and 3 percent in the Calcium triplet region, with no evidence of any changes visible between the two epochs in the lines.

We will continue to monitor the object. We would like to thank Drs Klaas Wiersema (Leicester) and Grant Kennedy (Cambridge) for bringing the notification of the current dip to our attention.
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 05/21/2017 09:20 PM
Potential reddening observed;

https://twitter.com/tsboyajian/status/866390381063229441
Quote
More dippy in B, lesser so in i'
Title: Re: Boyajians Star Updates And Discussion
Post by: Orbiter on 05/21/2017 09:26 PM
More dimming in the blue channels is strongly suggestive of dust.
Title: Re: Boyajians Star Updates And Discussion
Post by: Mongo62 on 05/21/2017 09:27 PM
So more absorption towards the blue, but little or no change to spectral lines? Sounds like dust involved to at least some degree, but no gas.
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 05/21/2017 09:35 PM
So more absorption towards the blue, but little or no change to spectral lines? Sounds like dust involved to at least some degree, but no gas.

Not necessarily no gas; a small (additional) amount of gas can be very hard to detect (high SNR and spectral resolution are needed).
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/21/2017 09:35 PM
More dimming in the blue channels is strongly suggestive of dust.

So after all that it's just a lot of dust. Mind you it must be an absolutely enormous amount to create these kind of dimming events.
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 05/21/2017 09:43 PM
More dimming in the blue channels is strongly suggestive of dust.

So after all that it's just a lot of dust. Mind you it must be an absolutely enormous amount to create these kind of dimming events.

It actually takes surprisingly little - small dust grains are very efficient at blocking light. But the absence of excess IR is a problem with dust theory.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/21/2017 09:50 PM
More dimming in the blue channels is strongly suggestive of dust.

So after all that it's just a lot of dust. Mind you it must be an absolutely enormous amount to create these kind of dimming events.

It actually takes surprisingly little - small dust grains are very efficient at blocking light. But the absence of excess IR is a problem with dust theory.

Mind you wouldn't it have to be something like 50% difference for it to be dust and we don't have those figures.
Title: Re: Boyajians Star Updates And Discussion
Post by: Mongo62 on 05/21/2017 10:07 PM
More dimming in the blue channels is strongly suggestive of dust.

So after all that it's just a lot of dust. Mind you it must be an absolutely enormous amount to create these kind of dimming events.

It actually takes surprisingly little - small dust grains are very efficient at blocking light. But the absence of excess IR is a problem with dust theory.

The extra dimming toward blue wavelengths suggests dust all right -- but how much dust? The lack of excess IR suggests minimal dust. Could most of the dimming be due to larger solid objects (pebble sized and up), with just enough dust present to cause the observed extra dimming toward blue wavelengths?
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 05/21/2017 10:12 PM
What would a Dyson swarm look like? Since a Dyson sphere is potentially physically impossible to construct, Dyson swarms in groups of varying size was probably always the more likely option if one went with the artificial construct idea.

So if these hypothetical swarms consist of vast formations of small individual components, could it produce some of the results we are seeing?
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/21/2017 10:20 PM
What would a Dyson swarm look like? Since a Dyson sphere is potentially physically impossible to construct, Dyson swarms in groups of varying size was probably always the more likely option if one went with the artificial construct idea.

So if these hypothetical swarms consist of vast formations of small individual components, could it produce some of the results we are seeing?
Is that because a Dyson sphere would collapse under its own mass?
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 05/21/2017 10:24 PM
I read that it would be very difficult for the sphere to maintain a stable position around the fully enclosed star. If it drifted slightly off centre, well, the consequences can be imagined.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/21/2017 10:34 PM
I read that it would be very difficult for the sphere to maintain a stable position around the fully enclosed star. If it drifted slightly off centre, well, the consequences can be imagined.
People jumping onto the dust explanation without the figures seems a bit premature. As far as I am aware there should actually be quite a big dip of about 50% in the data for it to be dust.
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 05/21/2017 10:54 PM
But the absence of excess IR is a problem with dust theory.
AFAIK, no IR results have been reported with the dip in progress yet, so things like the original comet scenario could still work. There may be other ways to keep dust below the current detection limits if it isn't in a system wide debris disk.

What would a Dyson swarm look like?
The simplest version is totally opaque objects, which would result in visible wavelengths dimming by the same amount. Reddening in visible wavelengths would seem to disfavor this. Assuming the aliens follow the laws of thermodynamics there still has to be some IR somewhere, but not necessarily enough for us to detect. Of course, with aliens you can fit almost any observation if you are willing to do enough special pleading.
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 05/21/2017 10:56 PM
Since we are speculating wildly one could also speculate whether clouds of dust would not be a by product of mega scale construction activities in a solar system.

If the 20% dip is a megastructure, maybe the smaller dips are dust clouds left over from the planetoids used as construction material.
Title: Re: Boyajians Star Updates And Discussion
Post by: jgoldader on 05/22/2017 12:37 AM
Observing in the IR from the ground is hard. If dust is the culprit, IR extinction (in magnitudes) is ~0.1 of visual extinction at 2.2 microns (K-band).  If it's dust in the present event, the visual extinction of ~0.03 mag becomes 0.003 mag in K-band, and AFAIK, photometry of that precision (including calibration) hasn't been done from the ground.  A drop of 3% visual due to some sort of solid body transit (not dust) would give a 3% IR drop.  You can't hope for much better accuracy than that in the case of ground-based photometry.  So with only a 3% event, I doubt you can get anything conclusive.

(Why is IR hard?  Short time scale variations in atmospheric opacity show up as a systematic calibration uncertainty that's generally well worse than the S/N of the observations of bright sources.  The edges of the IR observing bands are defined by strong molecular absorption features in our atmosphere, water being the main offender in the near-IR.  More water vapor= a smaller effective bandpass, hence less light getting to you.  If you watch a star all night in the IR, you see small variations in its brightness due to that.  And we're not even talking the effect of looking through varying air column thicknesses as the star rises, crosses the meridian, and sets.  Back in the day, we were happy with a couple percent systematic calibration uncertainty.  I have no idea if there's a star close enough to KIC that you could do differential photometry, comparing two stars in the same image to look for relative, not absolute, changes in brightness.  That would help deal with the atmospheric effects.  But you'd need to have established the differential brightness already for comparison.)

But the ideal case would be an event of, say, 10% visual flux drop, where you can believe the IR well enough to say whether the IR has gone down 1% (it's dust reddening) or 10% (it's akin to a transit).  This current event might not get that deep, but the ground-based photometry we've been shown  is pretty compelling evidence supporting the Kepler flux drops, and the new event, if it is real as it appears to be, shows the transits or whatever they are have not ended.  So, patience might reward us with a deep enough event that the IR observations become conclusive.

The lack of anything in the visual spectroscopy strikes me as inconclusive, unless I'm missing something.  I'd think a change of 3% in visual extinction (if it's dust) ought to give minuscule changes in the absorption line depths.  The lack of anything like emission lines appearing in the cores of the stellar absorption features might rule out some explanations involving unexpected stellar activity, but I haven't followed the literature enough to know for sure.
Title: Re: Boyajians Star Updates And Discussion
Post by: Bubbinski on 05/22/2017 12:38 AM
Is it also possible that the material that's blocking the starlight could be the remnants of a collision between two planets?
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 05/22/2017 02:08 AM
Is it also possible that the material that's blocking the starlight could be the remnants of a collision between two planets?
That was considered in the original Boyajian et al paper (https://arxiv.org/abs/1509.03622) paper, but disfavored because it should produce a lot of dust, which should show up as an IR excess. That's one reason they favored the comet scenario.

Subsequent observations confirmed and further constrained the lack of dust:
Marengo et al - KIC 8462852 - The Infrared Flux (https://arxiv.org/abs/1511.07908) (Spitzer)
Liss et al - IRTF/SPEX Observations of the Unusual Kepler Lightcurve System KIC8462852 (https://arxiv.org/abs/1512.00121)
Thompson et al - Constraints on the circumstellar dust around KIC 8462852 (https://arxiv.org/abs/1512.03693) (SCUBA-2 and SMA)

Neither planetary collision nor comets would obviously explain the long term dimming.
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 05/22/2017 05:37 AM
But the absence of excess IR is a problem with dust theory.
AFAIK, no IR results have been reported with the dip in progress yet, so things like the original comet scenario could still work. There may be other ways to keep dust below the current detection limits if it isn't in a system wide debris disk.

Right, but IR emission from circumstellar dust ought to be there also when the dust is not transiting between us and the star. There are ways to keep IR at a level where it would be below current upper limits, but they're getting a bit contrived.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/22/2017 07:42 AM
I have been following this on Reddit & now got throughly confused as there's so much contradictory theorising on there it's doing my head in.
Title: Re: Boyajians Star Updates And Discussion
Post by: high road on 05/22/2017 11:28 AM
Yay for science. Let's find out what rare natural event is causing this.

Somehow, I don't think TakeOff is convinced that this isn't due to distributed equipment failure or people finding what they want to find. :p
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/22/2017 12:07 PM
Yay for science. Let's find out what rare natural event is causing this.

Somehow, I don't think TakeOff is convinced that this isn't due to distributed equipment failure or people finding what they want to find. :p

Assume nothing.
Title: Re: Boyajians Star Updates And Discussion
Post by: moreno7798 on 05/22/2017 12:43 PM
There's probably going to be some dimming from dust but the key is going to be the spectra from the big dip. What the spectra says from the big dip is I believe what's going to solve the mystery. But I'm inclined to think that there's not going to be a cut and dry explanation and we're going to have to work to solve some unexplained causes and or effects.

I was wondering if all of the Kepler data has been combed through? It might help to solve this mystery if we find another star with similar dimming events.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/22/2017 12:48 PM
I was wondering if all of the Kepler data has been combed through? It might help to solve this mystery if we find another star with similar dimming events.

Yes, many times.  This is a unique star, though it shows some similarities to "YSO dippers" (but it shows none of the features of being a young star).

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Orbiter on 05/22/2017 12:58 PM
I was wondering if all of the Kepler data has been combed through? It might help to solve this mystery if we find another star with similar dimming events.

Yes, many times.  This is a unique star, though it shows some similarities to "YSO dippers" (but it shows none of the features of being a young star).

--- Tony


Yea, which is why the ultimate explanation will probably be one that's really interesting even without the ETI explanation. If it's just a big asteroid belt then astronomers would have noticed this with other F-sequence stars throughout the Kepler mission. The "planet eating" hypothesis is still my favorite natural explanation.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/22/2017 01:13 PM
I was wondering if all of the Kepler data has been combed through? It might help to solve this mystery if we find another star with similar dimming events.

Yes, many times.  This is a unique star, though it shows some similarities to "YSO dippers" (but it shows none of the features of being a young star).

--- Tony


Yea, which is why the ultimate explanation will probably be one that's really interesting even without the ETI explanation. If it's just a big asteroid belt then astronomers would have noticed this with other F-sequence stars throughout the Kepler mission. The "planet eating" hypothesis is still my favorite natural explanation.

It's probably more than one phenomena which is why it's so difficult to resolve.

Problem with the planet eating theory is it doesn't resolve the matter of the long term dimming of the star that maybe occurring. On that I am more inclined to believe the guy who says it is dimming long term than the one who doesn't.
Title: Re: Boyajians Star Updates And Discussion
Post by: Orbiter on 05/22/2017 01:46 PM
I was wondering if all of the Kepler data has been combed through? It might help to solve this mystery if we find another star with similar dimming events.

Yes, many times.  This is a unique star, though it shows some similarities to "YSO dippers" (but it shows none of the features of being a young star).

--- Tony


Yea, which is why the ultimate explanation will probably be one that's really interesting even without the ETI explanation. If it's just a big asteroid belt then astronomers would have noticed this with other F-sequence stars throughout the Kepler mission. The "planet eating" hypothesis is still my favorite natural explanation.

It's probably more than one phenomena which is why it's so difficult to resolve.

Problem with the planet eating theory is it doesn't resolve the matter of the long term dimming of the star that maybe occurring. On that I am more inclined to believe the guy who says it is dimming long term than the one who doesn't.

As I understand it, Dr. Wright put for an idea shown in one model that the long-term dimming could be a result of the star releasing energy after the collision over time during his video update on Friday. The short-term dimming would be the result of leftover material from that consumption orbiting the star in an elliptical, ~750 day orbit. You're probably right though that it's a combination of several factors resulting in the dimming.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/22/2017 01:50 PM
I was wondering if all of the Kepler data has been combed through? It might help to solve this mystery if we find another star with similar dimming events.

Yes, many times.  This is a unique star, though it shows some similarities to "YSO dippers" (but it shows none of the features of being a young star).

--- Tony


Yea, which is why the ultimate explanation will probably be one that's really interesting even without the ETI explanation. If it's just a big asteroid belt then astronomers would have noticed this with other F-sequence stars throughout the Kepler mission. The "planet eating" hypothesis is still my favorite natural explanation.

It's probably more than one phenomena which is why it's so difficult to resolve.

Problem with the planet eating theory is it doesn't resolve the matter of the long term dimming of the star that maybe occurring. On that I am more inclined to believe the guy who says it is dimming long term than the one who doesn't.

As I understand it, Dr. Wright put for an idea shown in one model that the long-term dimming could be a result of the star releasing energy after the collision over time during his video update on Friday. The short-term dimming would be the result of leftover material from that consumption orbiting the star in an elliptical, ~750 day orbit. You're probably right though that it's a combination of several factors resulting in the dimming.

Problem is you can postulate a number of theories to generate this much dust from the natural to unnatural. Plus everyone seems to be generating theories off the limited data that's been released publicly unless I am missing something?

I really don't think this recent dip is going to resolve this matter.
Title: Re: Boyajians Star Updates And Discussion
Post by: RotoSequence on 05/22/2017 01:53 PM
I disagree; this recent dip is the beginning of resolving the matter. Spectroscopic data was necessary to create a firmer hypothesis - and the dimming itself was needed to put the "Kepler Instrumentation Issue" nonsense to rest. It will take time and probably get messier in the interim, but the new information is going to go a long way towards resolving what's happening.
Title: Re: Boyajians Star Updates And Discussion
Post by: Mongo62 on 05/22/2017 01:59 PM
Has there been any photometry of the most recent couple of days released? There had been talk of the dip continuing, and even increasing in depth again, but I have heard nothing new in that regard in about a day. Is the dip over, or is the light-curve continuing to fluctuate?
Title: Re: Boyajians Star Updates And Discussion
Post by: Orbiter on 05/22/2017 02:04 PM
Has there been any photometry of the most recent couple of days released? There had been talk of the dip continuing, and even increasing in depth again, but I have heard nothing new in that regard in about a day. Is the dip over, or is the light-curve continuing to fluctuate?

We haven't heard anything about the photometry of the star since Dr. Boyajian posted on Twitter that the star was dimming more in the blue channels than in the rest. They're still processing the data. We'll probably get more news today.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/22/2017 02:16 PM
Has there been any photometry of the most recent couple of days released? There had been talk of the dip continuing, and even increasing in depth again, but I have heard nothing new in that regard in about a day. Is the dip over, or is the light-curve continuing to fluctuate?

We haven't heard anything about the photometry of the star since Dr. Boyajian posted on Twitter that the star was dimming more in the blue channels than in the rest. They're still processing the data. We'll probably get more news today.

I wonder what the error bars on that pronouncement was?

The only thing that I believe has been resolved so far is the matter of if the original observations were a Kepler mechanical fault, which was always a BS theory to start with.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/22/2017 04:09 PM
Quote
Jason Wright @Astro_Wright
Latest photometry from last night; this event seems to have ended, but remember than in Q16 they came in clumps.
@tsboyajian

https://mobile.twitter.com/Astro_Wright/status/866677994173198336

Quote
Jason Wright @Astro_Wright
Back
48 missed calls
10 voicemails
5 from the same person asking if I've read his 1982 SETI paper yet, asking me to call or *mail* him

Paul Thompson @trailrunnerlife
Now my interest is piqued, sifting through Google Scholar for SETI research published in '82...this better be good

Jason Wright @Astro_Wright

Replying to @trailrunnerlife
Details may have been slightly changed to protect the guilty.

https://mobile.twitter.com/Astro_Wright/status/866692487355785217
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 05/22/2017 07:30 PM

The only thing that I believe has been resolved so far is the matter of if the original observations were a Kepler mechanical fault, which was always a BS theory to start with.

Yeah, it seems that many people on twitter, reddit and elsewhere have unrealistic expectations about what can be said (in just a few hours!) based on observations of a single, not particularly deep dip.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/22/2017 07:41 PM

The only thing that I believe has been resolved so far is the matter of if the original observations were a Kepler mechanical fault, which was always a BS theory to start with.

Yeah, it seems that many people on twitter, reddit and elsewhere have unrealistic expectations about what can be said (in just a few hours!) based on observations of a single, not particularly deep dip.

For me anyway refuting the nonsense that was implied about the people working on the Kepler mission is sufficient for now.
Title: Re: Boyajians Star Updates And Discussion
Post by: KelvinZero on 05/22/2017 11:10 PM
Isn't it initially appearing to be a very good fit for the Kepler data?
It appears to be a perfect match.
Hi.. is this a theory that the dip is a planet with a massive ring system? That was the first thing I thought looking at the symmetry. Then I noticed the little ringed planet drawn in the corner.

We should have a poll for the final explanation. My guess is "the remains of Alderaan". :-)
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/22/2017 11:26 PM
Isn't it initially appearing to be a very good fit for the Kepler data?
It appears to be a perfect match.
Hi.. is this a theory that the dip is a planet with a massive ring system? That was the first thing I thought looking at the symmetry. Then I noticed the little ringed planet drawn in the corner.

We should have a poll for the final explanation. My guess is "the remains of Alderaan". :-)

It would have to be a very big planet with an absolutely vast ring system.
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 05/22/2017 11:30 PM
Isn't it initially appearing to be a very good fit for the Kepler data?
It appears to be a perfect match.
Hi.. is this a theory that the dip is a planet with a massive ring system? That was the first thing I thought looking at the symmetry. Then I noticed the little ringed planet drawn in the corner.

We should have a poll for the final explanation. My guess is "the remains of Alderaan". :-)

It would have to be a very big planet with an absolutely vast ring system.

Interestingly this has just cropped up;

http://news.agu.org/press-release/researchers-propose-new-type-of-planetary-object/
Title: Re: Boyajians Star Updates And Discussion
Post by: savuporo on 05/23/2017 04:24 AM
For me anyway refuting the nonsense that was implied about the people working on the Kepler mission is sufficient for now.

I also thought that it may have been a weird software/instrument error on Kepler at first, 'twas dumb.
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 05/23/2017 04:41 AM
Isn't it initially appearing to be a very good fit for the Kepler data?
It appears to be a perfect match.
Hi.. is this a theory that the dip is a planet with a massive ring system? That was the first thing I thought looking at the symmetry. Then I noticed the little ringed planet drawn in the corner.

We should have a poll for the final explanation. My guess is "the remains of Alderaan". :-)

It would have to be a very big planet with an absolutely vast ring system.

Interestingly this has just cropped up;

http://news.agu.org/press-release/researchers-propose-new-type-of-planetary-object/

I just saw it as well.  They are calling it a "Synestia".  Here is the original paper.
http://onlinelibrary.wiley.com/store/10.1002/2016JE005239/asset/jgre20669.pdf;jsessionid=64AECF92E4C2C5B0389C0C0178E58B16.f01t02?v=1&t=j312c25b&s=dbc30a56f543a94c095b0339c6437f654e914766

The toroidal shape seems like it could match up to the Kepler observations.  Depending on the age & angular momentum of the synestia, the matter may have cooled enough so that it may explain the lack of IR excess.

the attached rendering is from this link:
https://wattsupwiththat.com/2017/05/22/astronomers-propose-a-new-type-of-planetary-object/
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 05/23/2017 05:11 AM
Isn't it initially appearing to be a very good fit for the Kepler data?
It appears to be a perfect match.
Hi.. is this a theory that the dip is a planet with a massive ring system? That was the first thing I thought looking at the symmetry. Then I noticed the little ringed planet drawn in the corner.

We should have a poll for the final explanation. My guess is "the remains of Alderaan". :-)

It would have to be a very big planet with an absolutely vast ring system.

I thought I recalled some of the early papers by J.Wright showed that the light curve of transiting planets had a markedly flat bottom when in full transit.  A ringed planet is not much different.  The rings, depending on orientation to the viewed during transit, may create a more shallow ingress and egress of the event.   The Kepler light curves for Tabby's star did not match what would be created by a ringed planet.  Diffuse/scattered objects, or massive megastructures work better to re-create the Kepler curves for Tabby's star.  That fact is why gathering of spectral data during transits is so important to solving this riddle.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/23/2017 06:23 AM
Glad he posted this considering the public interest in the topic.

Quote
Jason Wright @Astro_Wright
Replying to @zero132132 and 3 others
Right. We will make the data truly public eventually, somehow. Right now it's not mine to give away, and it's not in a final form we trust.

https://mobile.twitter.com/Astro_Wright/status/866826117071728643

Quote
Tabetha Boyajian @tsboyajian
Looking forward to what happens tonight with #tabbysstar . @kickstarter backers expect a full update tomorrow!

https://mobile.twitter.com/tsboyajian/status/866835203456724994
Title: Re: Boyajians Star Updates And Discussion
Post by: sghill on 05/23/2017 11:14 AM
Since we're speculating,  what would it look like if an icy giant gas planet regularly gets too close to a larger gas giant in orbit? Would it shed gas towards the larger body in a predictable spiral in a manner that we are now witnessing? Like two binary stars where one is parasitic, but much smaller and cooler, and the gas is replenished on a regular cycle, so you'd get a "hole", and then a "screen" pattern like in the previous "Synestia" image here: http://forum.nasaspaceflight.com/index.php?topic=41704.msg1681766#msg1681766

.

Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/23/2017 02:05 PM
Can anyone estimate why Jason Wright would be after this info?

Quote
1h
Jason Wright @Astro_Wright
Astro hive-mind:
How do I get an ephemeris for @NASAKepler from @NASAJPL Horizons? I want x,y,z in barycentric frame.

Jason Wright @Astro_Wright

Replying to @Astro_Wright and 2 others
I tried getting distance, RA, DEC from vantage of SSB (site @0) but I get "Barycentric OBSERVER table disallowed -- consider body-center 10"

https://mobile.twitter.com/Astro_Wright/status/866995929236287488
Title: Re: Boyajians Star Updates And Discussion
Post by: jgoldader on 05/23/2017 02:41 PM
Can anyone estimate why Jason Wright would be after this info?

Quote
1h
Jason Wright @Astro_Wright
Astro hive-mind:
How do I get an ephemeris for @NASAKepler from @NASAJPL Horizons? I want x,y,z in barycentric frame.

Jason Wright @Astro_Wright

Replying to @Astro_Wright and 2 others
I tried getting distance, RA, DEC from vantage of SSB (site @0) but I get "Barycentric OBSERVER table disallowed -- consider body-center 10"

https://mobile.twitter.com/Astro_Wright/status/866995929236287488

When you're looking at transits/occultations/etc., the time the observer sees the event depends on the location of the observer, because the light travel time from the event itself to the observer depends on the position of the observer.  Suppose one observer on Earth was looking at, oh, say an extrasolar planet transiting its star.  That observer would probably measure different ingress/egress times than would, say, the Kepler satellite, because the Earth and Kepler are most likely at different distances from the event.

For occultations/transits/etc., I believe the general practice is to correct times to heliocentric julian date, though perhaps they're using the solar system barycenter (which is what I suspect the "SSB" means).  So it would seem somebody's looking to transform the time of an observation made by Kepler, to the time the light would have been seen by an observer at the solar system barycenter, or perhaps vice versa.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/23/2017 02:43 PM
Can anyone estimate why Jason Wright would be after this info?

Quote
1h
Jason Wright @Astro_Wright
Astro hive-mind:
How do I get an ephemeris for @NASAKepler from @NASAJPL Horizons? I want x,y,z in barycentric frame.

Jason Wright @Astro_Wright

Replying to @Astro_Wright and 2 others
I tried getting distance, RA, DEC from vantage of SSB (site @0) but I get "Barycentric OBSERVER table disallowed -- consider body-center 10"

https://mobile.twitter.com/Astro_Wright/status/866995929236287488

When you're looking at transits/occultations/etc., the time the observer sees the event depends on the location of the observer, because the light travel time from the event itself to the observer depends on the position of the observer.  Suppose one observer on Earth was looking at, oh, say an extrasolar planet transiting its star.  That observer would probably measure different ingress/egress times than would, say, the Kepler satellite, because the Earth and Kepler are most likely at different distances from the event.

For occultations/transits/etc., I believe the general practice is to correct times to heliocentric julian date, though perhaps they're using the solar system barycenter (which is what I suspect the "SSB" means).  So it would seem somebody's looking to transform the time of an observation made by Kepler, to the time the light would have been seen by an observer at the solar system barycenter, or perhaps vice versa.

Thank you.

You'd think JPL might have software that can work this out for investigators/researchers.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/23/2017 03:28 PM
For occultations/transits/etc., I believe the general practice is to correct times to heliocentric julian date, though perhaps they're using the solar system barycenter (which is what I suspect the "SSB" means).  So it would seem somebody's looking to transform the time of an observation made by Kepler, to the time the light would have been seen by an observer at the solar system barycenter, or perhaps vice versa.

Kepler uses Barycentric Julian Date

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: JasonAW3 on 05/23/2017 06:07 PM
I may have missed it, but has the star started brightening again yet?
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/23/2017 06:44 PM
I may have missed it, but has the star started brightening again yet?

It's back to normal at the moment.

Quote
Tabetha Boyajian @tsboyajian

Replying to @Apnoespock and @kickstarter
we have a few holes, and of course weather gets in the way too, but we have been fortunate over that

https://mobile.twitter.com/tsboyajian/status/867060889056403456
Title: Re: Boyajians Star Updates And Discussion
Post by: JasonAW3 on 05/23/2017 08:07 PM
I may have missed it, but has the star started brightening again yet?

It's back to normal at the moment.

Quote
Tabetha Boyajian @tsboyajian

Replying to @Apnoespock and @kickstarter
we have a few holes, and of course weather gets in the way too, but we have been fortunate over that

https://mobile.twitter.com/tsboyajian/status/867060889056403456

So I guesx that they don't hve the light curve and duration figures compiled just yet.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/23/2017 08:08 PM
I may have missed it, but has the star started brightening again yet?

It's back to normal at the moment.

Quote
Tabetha Boyajian @tsboyajian

Replying to @Apnoespock and @kickstarter
we have a few holes, and of course weather gets in the way too, but we have been fortunate over that

https://mobile.twitter.com/tsboyajian/status/867060889056403456

So I guesx that they don't hve the light curve and duration figures compiled just yet.

Sounds like they are working on it with the Kickstart supporters first in line for an update.
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 05/24/2017 02:41 AM
New paper KIC 8462852: Will the Trojans return in 2021? (https://arxiv.org/abs/1705.08427) Fernando J. Ballesteros, Pablo Arnalte-Mur, Alberto Fernandez-Soto, Vicent J. Martinez (submitted, not yet reviewed / accepted)

Quote
KIC 8462852 stood out among more than 100,000 stars in the Kepler catalogue because of the strange features of its light curve: a wide and asymmetric dimming taking up to 15 per cent of the total light, together with a period of multiple, narrow dimmings happening approximately 700 days later. Several models have been proposed to account for this abnormal behaviour, most of which require either unlikely causes or a finely-tuned timing. We aim at offering a relatively natural solution, invoking only phenomena that have been previously observed, although perhaps in larger or more massive versions. We model the system using a large, ringed body whose transit produces the first dimming and a swarm of Trojan objects sharing its orbit that causes the second period of multiple dimmings. The resulting orbital period is T≈12 years, with a semi-major axis a≈6 au. In this context the recent observation of a minor dimming can be explained as a secondary eclipse produced by the passage of the planet behind the star. Our model allows us to make two straightforward predictions: we expect the passage of a new swarm of Trojans in front of the star starting during the early months of 2021, and a new transit of the main object during the first half of 2023.

Trojans are a clever way to get a ~700 day period without having the dust warm enough to exceed observational limits, but the trojan clouds need to be extremely massive and/or dusty. The larger orbit also greatly relaxes constraints from radial velocity. The authors specifically note that it doesn't address the long term dimming. They suggest the most recent dip is compatible with a secondary eclipse of the planet.

My overall impression is interesting and not totally implausible, but not really satisfying.
Title: Re: Boyajians Star Updates And Discussion
Post by: launchwatcher on 05/24/2017 04:43 AM
Since we're speculating,  what would it look like if an icy giant gas planet regularly gets too close to a larger gas giant in orbit?

I would assume a close pass would perturb the orbits of both bodies so it wouldn't keep happening.   It might even eject the smaller planet entirely...
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 05/24/2017 06:04 AM
New paper KIC 8462852: Will the Trojans return in 2021? (https://arxiv.org/abs/1705.08427) Fernando J. Ballesteros, Pablo Arnalte-Mur, Alberto Fernandez-Soto, Vicent J. Martinez (submitted, not yet reviewed / accepted)

Quote
KIC 8462852 stood out among more than 100,000 stars in the Kepler catalogue because of the strange features of its light curve: a wide and asymmetric dimming taking up to 15 per cent of the total light, together with a period of multiple, narrow dimmings happening approximately 700 days later. Several models have been proposed to account for this abnormal behaviour, most of which require either unlikely causes or a finely-tuned timing. We aim at offering a relatively natural solution, invoking only phenomena that have been previously observed, although perhaps in larger or more massive versions. We model the system using a large, ringed body whose transit produces the first dimming and a swarm of Trojan objects sharing its orbit that causes the second period of multiple dimmings. The resulting orbital period is T≈12 years, with a semi-major axis a≈6 au. In this context the recent observation of a minor dimming can be explained as a secondary eclipse produced by the passage of the planet behind the star. Our model allows us to make two straightforward predictions: we expect the passage of a new swarm of Trojans in front of the star starting during the early months of 2021, and a new transit of the main object during the first half of 2023.

Trojans are a clever way to get a ~700 day period without having the dust warm enough to exceed observational limits, but the trojan clouds need to be extremely massive and/or dusty. The larger orbit also greatly relaxes constraints from radial velocity. The authors specifically note that it doesn't address the long term dimming. They suggest the most recent dip is compatible with a secondary eclipse of the planet.

My overall impression is interesting and not totally implausible, but not really satisfying.

The secondary eclipse explanation feels a bit suspect. I don't see why the light curve would be so flat right until the secondary eclipse happens while the phase angle keeps changing.

edit: What I mean is that if a non-negligible fraction of observed flux in 'normal' state is scattered off planet/rings, I think there should be more modulation throughout the Kepler lightcurve as the planet moves around its orbit.
Title: Re: Boyajians Star Updates And Discussion
Post by: high road on 05/24/2017 07:04 AM
I may have missed it, but has the star started brightening again yet?

It's back to normal at the moment.


Well, for this particular star, 'normal' means it's back to dimming slowly rather than dipping fast.  ;)
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/24/2017 07:27 AM
My overall impression is interesting and not totally implausible, but not really satisfying.

Yes, interesting but I think it has some serious issues:
- the proposed planet has a radius ~5RJ.  That makes is a star which we'd see in IR at minimum
- the asymmetry of the supposed primary transit worries me. Impact parameter b = ~0.6 I understand, but I don't think rings really explain the smooth but asymmetric ingress and egress.
- others have mentioned ring stability. These are huge, covering most of the Hill sphere I think; hard to see how they're stable
- as stated in the paper, it does not explain the secular decline
- as as58 above, I'm dubious about the secondary as well

Edit: more on the secondary. For it to be a 3% dip says there is a LOT of reflected light, so yes, I'd expect phase modulation.

Edit2: perhaps we *are* seeing phase modulation.  See  figure 3 of Ben Montet's paper (https://arxiv.org/abs/1608.01316).

But nevertheless, it is still interesting ...

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/24/2017 07:28 AM
Sounds like they are working on it with the Kickstart supporters first in line for an update.

Sadly, I won't see the update until tomorrow as I don't have access to the right email until I get home :-/

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 05/24/2017 07:44 AM
Not a lot of new info yet. Just the data showing the event is pretty much over and a photo of the whiteboard showing many of the facilities that got data, which is a bit more than has been already stated. Tabby does say there should be short but regular updates in due course.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/24/2017 07:50 AM
Be interesting to see if it now goes into a vast dip because the best fit that Jason Wright was suggesting for this dip, last time I saw from the Kepler data was just before one of these.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/24/2017 07:52 AM
Be interesting to see if it now goes into a vast dip because the best fit that Jason Wright was suggesting for this dip, last time I saw from the Kepler data was just before one of these.

Yes indeed. That is the good thing about the rings + trojans idea: it is eminently testable!

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 05/24/2017 08:14 AM
Edit2: perhaps we *are* seeing phase modulation.  See  figure 3 of Ben Montet's paper (https://arxiv.org/abs/1608.01316).

I'm not seeing phase modulation in that figure, or at least nothing consistent with a ~700 day period orbit...
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/24/2017 08:31 AM
Edit2: perhaps we *are* seeing phase modulation.  See  figure 3 of Ben Montet's paper (https://arxiv.org/abs/1608.01316).

I'm not seeing phase modulation in that figure, or at least nothing consistent with a ~700 day period orbit...

Agreed on the ~700 days. 

However, the inclined rings + trojans idea implies a ~12 year period, in which case what I was thinking was that the dip in the 2nd half of the figure could be when the proposed rings transition from being reflective to being transmissive. However, I've done no modelling of this ...

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/24/2017 08:44 AM
This planet seems ludicrously big more or less than M-Dwarf which I'd thought would be likely  beyond the fusion limit. Also Saturn's rings are bright in IR believe. So all this suggests this object would be plenty visible in IR, yet we've seen nothing of this. Also wouldn't a planet like this give the star a noticeable wobble.
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 05/24/2017 08:51 AM
Edit2: perhaps we *are* seeing phase modulation.  See  figure 3 of Ben Montet's paper (https://arxiv.org/abs/1608.01316).

I'm not seeing phase modulation in that figure, or at least nothing consistent with a ~700 day period orbit...

Agreed on the ~700 days. 

However, the inclined rings + trojans idea implies a ~12 year period, in which case what I was thinking was that the dip in the 2nd half of the figure could be when the proposed rings transitions from being reflective to being transmissive. However, I've done no modelling of this ...

--- Tony

Ok, I see. But if that dip is interpreted as rings transiting the star, the timescale looks too long (already ~2 years and doesn't look like it's even half way through when Kepler stopped taking data).
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/24/2017 09:02 AM
Edit2: perhaps we *are* seeing phase modulation.  See  figure 3 of Ben Montet's paper (https://arxiv.org/abs/1608.01316).

I'm not seeing phase modulation in that figure, or at least nothing consistent with a ~700 day period orbit...

Agreed on the ~700 days. 

However, the inclined rings + trojans idea implies a ~12 year period, in which case what I was thinking was that the dip in the 2nd half of the figure could be when the proposed rings transitions from being reflective to being transmissive. However, I've done no modelling of this ...

--- Tony

Ok, I see. But if that dip is interpreted as rings transiting the star, the timescale looks too long (already ~2 years and doesn't look like it's even half way through when Kepler stopped taking data).

That wasn't quite what I meant ... and I've realised what I wrote confused two distinct parts of the amorphous idea floating around inside my addled brain :-)

To expand on what I was thinking:
- for a large fraction of the orbit, starlight reflects from the rings, declining slowly as the reflection angle changes, which you see in the first half of figure 3.
- when the reflection angle reaches a critical value, the reflected light drops off sharply and we're just seeing the light of the star.
- when the planet + rings *actually* transit, you get a drop-off due to both the planet and the rings
- and this accounts for the apparently large radius in the paper (~5RJ) of the supposed primary transit
- it also accounts for why we see such a large secondary transit

Problems with this include:
- lack of detected IR emissions, though I think we only ruled out IR from dust
- the shape of the asymmetric primary transit.  Not sure a planet + inclined rings really explains this
- the long term secular decline from Shaefer et al.

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 05/24/2017 09:25 AM
Problems with this include:
- lack of detected IR emissions, though I think we only ruled out IR from dust
- the shape of the asymmetric primary transit.  Not sure a planet + inclined rings really explains this
- the long term secular decline from Shaefer et al.

I'll just add a couple ;)

- Planetary ring system, which reflects at times at least ~3% of the total stellar flux, sounds... large. And reflective in backscattering direction.
- If the recent dip were the secondary eclipse, it being deeper in blue than in red doesn't follow naturally (as it does if the dip were caused by transiting dust). Maybe it could be done with just the right kind of ring particles to get the albedo and backscatter just so, but it feels contrived.
- It looks to me (not that I've checked that closely) that the relative timings of supposed primary and secondary eclipses and orbital phase modulated ring reflection don't match up that well.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/24/2017 09:41 AM
Yes, lots of problems. I was just musing really to see if it could be made to fit more of the known data (i.e. Montet et al).

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Req on 05/24/2017 10:05 AM
Just attaching an image as a visual aid to the conversation.

As has already been mentioned, despite any problems one thing that is nice is that it makes a solid prediction, which also means it should be easy to falsify it even before 2021, possibly very soon.

Edit to add this snippet from Wikipedia to give a bit of detail about secondary eclipses for those who are wondering:
Quote
Additionally, the secondary eclipse (when the planet is blocked by its star) allows direct measurement of the planet's radiation and helps to constrain the planet's eccentricity without the presence of other planets. If the star's photometric intensity during the secondary eclipse is subtracted from its intensity before or after, only the signal caused by the planet remains.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/24/2017 10:18 AM
A solid but pretty contrived prediction.
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 05/24/2017 10:32 AM
Btw this pre-print dropped on Arxiv yesterday arguing a Solar System cause;  https://arxiv.org/abs/1705.08377

I must admit the first thing I was thinking when Wright was asking about finding Kepler's position in the barycentric frame was some kind of Solar System argument regarding lines of sight.
Title: Re: Boyajians Star Updates And Discussion
Post by: Req on 05/24/2017 10:55 AM
Btw this pre-print dropped on Arxiv yesterday arguing a Solar System cause;  https://arxiv.org/abs/1705.08377

I must admit the first thing I was thinking when Wright was asking about finding Kepler's position in the barycentric frame was some kind of Solar System argument regarding lines of sight.

Interesting.  It gives the example of a ring with a "thickness" of 600,000km or greater at ~50AU in the Kuiper belt as an explanation for both the Kepler and earth-based observations.
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 05/24/2017 12:02 PM
Btw this pre-print dropped on Arxiv yesterday arguing a Solar System cause;  https://arxiv.org/abs/1705.08377

I must admit the first thing I was thinking when Wright was asking about finding Kepler's position in the barycentric frame was some kind of Solar System argument regarding lines of sight.

Interesting.  It gives the example of a ring with a "thickness" of 600,000km or greater at ~50AU in the Kuiper belt as an explanation for both the Kepler and earth-based observations.

Presumably such a ring would be orbiting the Sun? So how would it ever repeat a dip, as it would likely move out of our line of sight with Tabby's star pretty quickly.
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 05/24/2017 12:38 PM
Btw this pre-print dropped on Arxiv yesterday arguing a Solar System cause;  https://arxiv.org/abs/1705.08377

I must admit the first thing I was thinking when Wright was asking about finding Kepler's position in the barycentric frame was some kind of Solar System argument regarding lines of sight.

Some initial thoughts from Wright on both these new papers;

http://sites.psu.edu/astrowright/2017/05/24/two-new-tabbys-star-papers/
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/24/2017 12:55 PM
Btw this pre-print dropped on Arxiv yesterday arguing a Solar System cause;  https://arxiv.org/abs/1705.08377

I must admit the first thing I was thinking when Wright was asking about finding Kepler's position in the barycentric frame was some kind of Solar System argument regarding lines of sight.

Some initial thoughts from Wright on both these new papers;

http://sites.psu.edu/astrowright/2017/05/24/two-new-tabbys-star-papers/

He doesn't exactly sound impressed by either paper though he is diplomatic about it. I especially like his comment that they have a really nice diagram.
Title: Re: Boyajians Star Updates And Discussion
Post by: kevin-rf on 05/24/2017 02:07 PM
Just attaching an image as a visual aid to the conversation.

As has already been mentioned, despite any problems one thing that is nice is that it makes a solid prediction, which also means it should be easy to falsify it even before 2021, possibly very soon.

Edit to add this snippet from Wikipedia to give a bit of detail about secondary eclipses for those who are wondering:
Quote
Additionally, the secondary eclipse (when the planet is blocked by its star) allows direct measurement of the planet's radiation and helps to constrain the planet's eccentricity without the presence of other planets. If the star's photometric intensity during the secondary eclipse is subtracted from its intensity before or after, only the signal caused by the planet remains.
More a question, if we are looking at objects with a 12 year instead of 750 day orbit, does that mean they would be much smaller for the same effect than a single onject with a 750 day orbit? So for the deep dip, it doesn't need to be three Jupiters in size? Just an observation...
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 05/24/2017 02:15 PM
A solid but pretty contrived prediction.
.  Even at 6-7 Au,  something with the mass required in this scenario just might be detectable by radial velocity measurements. 
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/24/2017 02:17 PM
A solid but pretty contrived prediction.
.  Even at 6-7 Au,  something with the mass required in this scenario just might be detectable by radial velocity measurements.

But hadn't that already been done with negative results?
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 05/24/2017 03:55 PM
I must admit the first thing I was thinking when Wright was asking about finding Kepler's position in the barycentric frame was some kind of Solar System argument regarding lines of sight.

Mine too. The exact position of Kepler should only be important if the occulter is much closer to Kepler than the star. But I don't see why the periodicity (if there really is any) is about two Kepler years instead of one.
Title: Re: Boyajians Star Updates And Discussion
Post by: jgoldader on 05/24/2017 04:37 PM
Btw this pre-print dropped on Arxiv yesterday arguing a Solar System cause;  https://arxiv.org/abs/1705.08377

I must admit the first thing I was thinking when Wright was asking about finding Kepler's position in the barycentric frame was some kind of Solar System argument regarding lines of sight.

I'd think that the many searches for gravitational lensing and occultations would rule out some large scale "ring" or other structure in the solar system.  And the recent event would likely put a damper on a solar system origin of the brightness drops.

I could buy that some TNO or whatever might've come apart out there and the bits traveled in front of KIC 8462852.  If that were true, I'd expect diffraction structure in the Kepler data though- fringing, maybe even central maximum and such- and there's none obvious in the Kepler data.  That Kepler didn't notice anything odd with other stars in the KIC 8462852 field would be another strike against a solar system origin; in hundreds of days of observation, I'd expect enough proper motion (Pluto moves over one degree per year, after all) that the bits in the debris field would wander over another star, and that apparently wasn't observed.
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 05/24/2017 06:47 PM
A solid but pretty contrived prediction.
.  Even at 6-7 Au,  something with the mass required in this scenario just might be detectable by radial velocity measurements.

But hadn't that already been done with negative results?

I recall it was looked at, however I don't know what interval they would have looked for shifted peaks in the spectra.  An object at 6-7 Au is typically not thought of as a candidate for detection by radial velocity methods, however I don't think anyone has ever considered a planet measuring .3 radii of an F class star, ( which must also be quite massive) with accompanying Trojan populations that have jupiter level masses.  The measurements would need to look for very long periodicities.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/24/2017 07:18 PM
A solid but pretty contrived prediction.
.  Even at 6-7 Au,  something with the mass required in this scenario just might be detectable by radial velocity measurements.

But hadn't that already been done with negative results?

I recall it was looked at, however I don't know what interval they would have looked for shifted peaks in the spectra.  An object at 6-7 Au is typically not thought of as a candidate for detection by radial velocity methods, however I don't think anyone has ever considered a planet measuring .3 radii of an F class star, ( which must also be quite massive) with accompanying Trojan populations that have jupiter level masses.  The measurements would need to look for very long periodicities.

The other problem is a ludicrously big planet with such a ring system and Trojan collection would not cause the long term fading of the star. Also would such a system exist around a more mature star. In the WASP example the huge rings will likely coalesce into moons in a number of million years it's believed.
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 05/24/2017 07:40 PM
A solid but pretty contrived prediction.
.  Even at 6-7 Au,  something with the mass required in this scenario just might be detectable by radial velocity measurements.

But hadn't that already been done with negative results?

I recall it was looked at, however I don't know what interval they would have looked for shifted peaks in the spectra.  An object at 6-7 Au is typically not thought of as a candidate for detection by radial velocity methods, however I don't think anyone has ever considered a planet measuring .3 radii of an F class star, ( which must also be quite massive) with accompanying Trojan populations that have jupiter level masses.  The measurements would need to look for very long periodicities.

The other problem is a ludicrously big planet with such a ring system and Trojan collection would not cause the long term fading of the star. Also would such a system exist around a more mature star. In the WASP example the huge rings will likely coalesce into moons in a number of million years it's believed.

Well, a further question I would have is that essentially three different unlikely occurrences are being proposed here, in conjunction, in order to try and explain the behavior of the star.

The existence of such a massive ringed planet is unlikely on its own. So is the existence of one such massive field of Trojan asteroids. And the existence of a second such field is the third unlikely occurrence.

Is there any reason why each of these three individual aspects would encourage the existence of the other two? In other words, a reason that would make the existence of all of these existing together more likely?

Otherwise I would find it strange why no other star has been observed with even one of the three aspects in place - a massive ringed planet of this size, or one Jupiter mass Trojan asteroid field. If none of these phenomena have even been observed in isolation anywhere else, what is the probability that they all would exist together around one star? Unless their origins can somehow be shown to be connected and inter-dependent.
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 05/24/2017 07:57 PM

Well, a further question I would have is that essentially three different unlikely occurrences are being proposed here, in conjunction, in order to try and explain the behavior of the star.

The existence of such a massive ringed planet is unlikely on its own. So is the existence of one such massive field of Trojan asteroids. And the existence of a second such field is the third unlikely occurrence.

Is there any reason why each of these three individual aspects would encourage the existence of the other two? In other words, a reason that would make the existence of all of these existing together more likely?

Otherwise I would find it strange why no other star has been observed with even merely one of the three aspects in place - a massive ringed planet of this size, or one Jupiter mass Trojan asteroid field. If none of these phenomenon have even been observed in isolation anywhere else, what is the probability that they all would exist together around one star? Unless their origins can somehow be shown to be connected and inter-dependent.

I share the objections you raised, as well as StarOne's. 

I think that the extreme behavior of the Boyajian's star dimming, something not observed anywhere else in the galaxy or universe, allows for unlikely, transient, & cataclysmic explanations.  The first order problem is fitting together an explanation for the light curve that is testable, & not reliant on the magic technology of aliens.   Once you have some candidate hypothesis, your can work it backward and forward in time to match (or not) the long term dimming & dynamic stability problems created by the proposed solution.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/24/2017 08:07 PM

Well, a further question I would have is that essentially three different unlikely occurrences are being proposed here, in conjunction, in order to try and explain the behavior of the star.

The existence of such a massive ringed planet is unlikely on its own. So is the existence of one such massive field of Trojan asteroids. And the existence of a second such field is the third unlikely occurrence.

Is there any reason why each of these three individual aspects would encourage the existence of the other two? In other words, a reason that would make the existence of all of these existing together more likely?

Otherwise I would find it strange why no other star has been observed with even merely one of the three aspects in place - a massive ringed planet of this size, or one Jupiter mass Trojan asteroid field. If none of these phenomenon have even been observed in isolation anywhere else, what is the probability that they all would exist together around one star? Unless their origins can somehow be shown to be connected and inter-dependent.

I share the objections you raised, as well as StarOne's. 

I think that the extreme behavior of the Boyajian's star dimming, something not observed anywhere else in the galaxy or universe, allows for unlikely, transient, & cataclysmic explanations.  The first order problem is fitting together an explanation for the light curve that is testable, & not reliant on the magic technology of aliens.   Once you have some candidate hypothesis, your can work it backward and forward in time to match (or not) the long term dimming & dynamic stability problems created by the proposed solution.

Not sure why people equate aliens with magic unless you think the evolution of other intelligent races is unnatural which is highly illogical.
Title: Re: Boyajians Star Updates And Discussion
Post by: matthewkantar on 05/24/2017 09:25 PM
Not sure why people equate aliens with magic unless you think the evolution of other intelligent races is unnatural which is highly illogical.

I think building a sphere or ring around a sun involves technology that we don't have. Especially if it isn't spilling lots of infrared or other energy out of the side away from the sun. Until demonstrated it might as well be called magic.

Matthew
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/24/2017 09:30 PM
Not sure why people equate aliens with magic unless you think the evolution of other intelligent races is unnatural which is highly illogical.

I think building a sphere or ring around a sun involves technology that we don't have. Especially if it isn't spilling lots of infrared or other energy out of the side away from the sun. Until demonstrated it might as well be called magic.

Matthew

I direct you towards this article.

https://medium.com/@mickdarling/think-like-an-alien-engineer-a3b974582d9b
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 05/24/2017 10:52 PM
Not sure why people equate aliens with magic unless you think the evolution of other intelligent races is unnatural which is highly illogical.

I think building a sphere or ring around a sun involves technology that we don't have. Especially if it isn't spilling lots of infrared or other energy out of the side away from the sun. Until demonstrated it might as well be called magic.

Matthew

I direct you towards this article.

https://medium.com/@mickdarling/think-like-an-alien-engineer-a3b974582d9b

Just to be clear, I'm not equating aliens to magic.   I'm saying that anything proposing aliens as the source of the dimming needs to be testable by existing laws of physics to be accepted, and not rely on invoking alien technology for shortfalls in what is observable.

edit:  to be fair, many non alien hypothesis have also relied on improbable conditions that are just as magical as invoking alien technology.  The comet swarm hypothesis delved into this territory at times.

Example:  The IR flux of the megastructures is invisible to us because aliens know infinitely more than we do, so they can somehow not reject their waste heat into space for us to see.

The article you referenced finished with a section on how to test for IR flux, my thoughts are the same.
Title: Re: Boyajians Star Updates And Discussion
Post by: KelvinZero on 05/25/2017 01:13 AM
Well, a further question I would have is that essentially three different unlikely occurrences are being proposed here, in conjunction, in order to try and explain the behavior of the star.
Layman opinion here, but aren't all three quite likely from some big single event that creates a big mess? I mean, if you start with a planet and turn it into a big cloud of rubble, there are 4 reasonable places for that rubble to accumulate: one dense point, a ring system around it, and swarms at the two trojans.

The lifespan of such a phenomenon might make it unlikely we would spot it, on the other hand I would have thought that every big mess that eventually coalesces into a planet or something would go through a moment like this: A dense point, a ring system, junk at the trojans.

(btw, if it is trojans, that will become fairly obvious from the fractional period I guess? We will know it is trojans or rule it out?)
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/25/2017 11:29 AM
Quote
Brooke Simmons @vrooje

The 2017-05-20 observers at @LickObservatory generously took data on #TabbysStar & I’ve just finished an initial reduction of the spectrum.

https://mobile.twitter.com/vrooje/status/867462206350163969

Quote
James Davenport @jradavenport
·
My morning's hack project: looking at #TabbysStar #BoyajiansStar with GALEX!
Interesting, but no new clues... yet!
jradavenport/GALEX_Boyajian
github.com

https://mobile.twitter.com/Astro_Wright/status/867569793343377409

Do these tell us anything much?

This Tweet intrigued me.

Quote
James Davenport @jradavenport

Replying to @ScottWFleming and 6 others
Peak from all visits combined. But by eye there is structure in first visit also

https://mobile.twitter.com/jradavenport/status/867589209694978048
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/25/2017 03:12 PM
Do these tell us anything much?

Only that the dip seen in the Kepler FFI images is (probably) also in the GALEX data ... note: don't assume this makes it achromatic; error bars are huge and there is uncertainty over things like zero point.

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/25/2017 03:28 PM
Do these tell us anything much?

Only that the dip seen in the Kepler FFI images is (probably) also in the GALEX data ... note: don't assume this makes it achromatic; error bars are huge and there is uncertainty over things like zero point.

--- Tony

Thank you for the explanation.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/25/2017 03:57 PM
AAVSO update.

https://www.aavso.org/aavso-alert-notice-579
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 05/25/2017 09:09 PM
I don't think GALEX has caught any of the real dips. They're discussing the secular dimming, in particular how it seems to have become faster in the last ~two years of Kepler observations. GALEX  seems to find similar (slightly larger) dimming in UV though as jebbo said, there are still questions about the GALEX calibration etc.
Title: Re: Boyajians Star Updates And Discussion
Post by: sghill on 05/26/2017 01:14 PM
This Tweet intrigued me.

Quote
James Davenport @jradavenport

Replying to @ScottWFleming and 6 others
Peak from all visits combined. But by eye there is structure in first visit also

https://mobile.twitter.com/jradavenport/status/867589209694978048

Oh God, he's going to regret using the word "structure" without considering how the Internet is going to react to that....
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/26/2017 04:59 PM
Quote
Tabetha Boyajian @tsboyajian

Replying to @lsu and @Bharat_J25
A2: This is the latest light curve up until an hour ago! #tabbysstar

https://mobile.twitter.com/tsboyajian/status/868135833286660096

Rest of the Q & A with Tabby.

https://mobile.twitter.com/tsboyajian
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/26/2017 09:44 PM
Montet doesn't believe it's a good fit for dust or solid objects.

https://mobile.twitter.com/benmontet/status/868201349351178240
Title: Re: Boyajians Star Updates And Discussion
Post by: Mongo62 on 05/27/2017 12:04 AM
A Theory for Tabby's Star (Without Aliens) | Metzger & Stone

https://www.youtube.com/watch?v=risNfZxz6DQ

This actually seams fairly plausible.
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 05/27/2017 02:34 AM
If they are proposing a planet impacted Tabby's star, wouldn't the stars spectra show evidence as with HIP68468?  HIP68468  shows heavier lithium emission lines as well as many other elements and metals common to planets, but not to the atmospheres of F class stars.  Or does it get around this by suggesting a KBO type planet that is primarily full of volatiles?
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 05/27/2017 05:12 AM
If they are proposing a planet impacted Tabby's star, wouldn't the stars spectra show evidence as with HIP68468?  HIP68468  shows heavier lithium emission lines as well as many other elements and metals common to planets, but not to the atmospheres of F class stars.  Or does it get around this by suggesting a KBO type planet that is primarily full of volatiles?
Skimming the Metzger et al paper (https://arxiv.org/abs/1612.07332), it doesn't seem to mention effect on the spectrum of the star at all, so that seems like a pretty good question. That seems like something that could potentially provide strong evidence in favor or against this theory, or at least add some constraints. FWIW, they have answered a some questions in the comments on the video, so it might be worth asking there.
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 05/27/2017 06:13 AM
If they are proposing a planet impacted Tabby's star, wouldn't the stars spectra show evidence as with HIP68468?  HIP68468  shows heavier lithium emission lines as well as many other elements and metals common to planets, but not to the atmospheres of F class stars.  Or does it get around this by suggesting a KBO type planet that is primarily full of volatiles?
Skimming the Metzger et al paper (https://arxiv.org/abs/1612.07332), it doesn't seem to mention effect on the spectrum of the star at all, so that seems like a pretty good question. That seems like something that could potentially provide strong evidence in favor or against this theory, or at least add some constraints. FWIW, they have answered a some questions in the comments on the video, so it might be worth asking there.

Here's the primary paper for HIP68468:
https://arxiv.org/abs/1610.09067

as well as an additional article:
http://www.sciencealert.com/scientists-have-found-evidence-of-a-planet-eating-death-star

I did ask the question in the comments of their video.  I hope they respond.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/27/2017 09:12 AM
This explanation seems to want to thread a lot of needles so to speak in an effort to fit theory to data.
Title: Re: Boyajians Star Updates And Discussion
Post by: Mongo62 on 05/27/2017 11:43 AM
This explanation seems to want to thread a lot of needles so to speak in an effort to fit theory to data.
True. But given how unusual this star appears to be, the actual reason for its behavior almost certainly did have to thread a lot of needles. I still cannot think of a more plausible non-megastructure explanation that explains both the sudden dips and the century-scale secular dimming.
Title: Re: Boyajians Star Updates And Discussion
Post by: high road on 05/28/2017 04:37 PM
Not sure why people equate aliens with magic unless you think the evolution of other intelligent races is unnatural which is highly illogical.

I think building a sphere or ring around a sun involves technology that we don't have. Especially if it isn't spilling lots of infrared or other energy out of the side away from the sun. Until demonstrated it might as well be called magic.

Matthew

Wouln't it be twice as mass efficient to radiate the heat perpendicular to the incoming sunlight?

I don't think aliens are causing this, but I'm getting annoyed by the offhand suggestion they would need non existant tech to do this. Just build a massive amount of orbital colonies and space power collectors in orbit around their main planet, with waste heat radiating perpendicular to their ecliptic (any other direction is blocked by other radiators) in both directions to explain for the big, irregular dimming event, and a slow but steady buildup of free space stations, mining activities and other power guzzlers for the slow dimming. Is that magic technology? Than what is this forum about.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/28/2017 06:29 PM
Quote
Tabetha Boyajian @tsboyajian

Replying to @FaustoPerra and @lsu
Whatever is occulting the star is ~the size of the star itself. Or larger.

https://mobile.twitter.com/tsboyajian/status/868208793615822848
Title: Re: Boyajians Star Updates And Discussion
Post by: Orbiter on 05/28/2017 06:35 PM
FWIW, there's precedence in our own solar system of coma's around comets growing to the size of the Sun. Comet Holmes' coma grew to a greater diameter than the Sun in 2007.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/28/2017 06:59 PM
FWIW, there's precedence in our own solar system of coma's around comets growing to the size of the Sun. Comet Holmes' coma grew to a greater diameter than the Sun in 2007.

I'd of thought a comet could only do this the once as by getting that close to the star to produce this kind of dimming it would either be eaten by the star or slingshotted out of the system.

Or you'd have to have a much, much larger comet than we see in our solar system to produce this effect with a more distant orbit.
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 05/28/2017 07:51 PM
Quote
Tabetha Boyajian @tsboyajian

Replying to @FaustoPerra and @lsu
Whatever is occulting the star is ~the size of the star itself. Or larger.

https://mobile.twitter.com/tsboyajian/status/868208793615822848

I want to understand that statement a bit better. If the largest dimming was 22%, and if the object is orbiting the star rather than in the interstellar medium hundreds of lightyears away from it, then why would it have to be the size of the star itself?

Would that not result in a 100% dimming, given that from our perspective the object is pretty much right on top of the star, rather than light years away from it?
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 05/28/2017 07:55 PM
I'd of thought a comet could only do this the once as by getting that close to the star to produce this kind of dimming it would either be eaten by the star or slingshotted out of the system.
Comets can break up and produce families. The Kreutz sungrazers are a good example. This could also potentially provide an explanation for quasi-periodic behavior: If a comet tends to fragment at perihelion, the large fragments have a limited range of separation velocities, so on the next perihelion passage, they have a characteristic separation distance. Families of fragments like this have been observed in our solar system.

Without additional external influences, a close encounter with the star will not "slingshot" them out of the system. Only interactions with additional bodies or non-gravitational forces can result in ejection.
Quote
Or you'd have to have a much, much larger comet than we see in our solar system to produce this effect with a more distant orbit.
There is nothing implausible about larger parent bodies than the comets we've seen in our very brief existence. On the contrary, it's virtually certain that much larger bodies occasionally get into cometary orbits. In our own system, Centaurs are unstable, so 200+ km objects like Chariklo must occasionally get scattered into the inner solar system. If the M dwarf near Boyajian's star really made a close approach, dislodging things the size of Ceres or Pluto or even full blown planets would not be extraordinary.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/28/2017 07:58 PM
I'd of thought a comet could only do this the once as by getting that close to the star to produce this kind of dimming it would either be eaten by the star or slingshotted out of the system.
Comets can break up and produce families. The Kreutz sungrazers are a good example. This could also potentially provide an explanation for quasi-periodic behavior: If a comet tends to fragment at perihelion, the large fragments have a limited range of separation velocities, so on the next perihelion passage, they have a characteristic separation distance. Families of fragments like this have been observed in our solar system.

Without additional external influences, a close encounter with the star will not "slingshot" them out of the system. Only interactions with additional bodies or non-gravitational forces can result in ejection.
Quote
Or you'd have to have a much, much larger comet than we see in our solar system to produce this effect with a more distant orbit.
There is nothing implausible about larger parent bodies than the comets we've seen in our very brief existence. On the contrary, it's virtually certain that much larger bodies occasionally get into cometary orbits. In our own system, Centaurs are unstable, so 200+ km objects like Chariklo must occasionally get scattered into the inner solar system. If the M dwarf near Boyajian's star really made a close approach, dislodging things the size of Ceres or Pluto or even full blown planets would not be extraordinary.

I though the M dwarf was deemed as too distant and that it's recent movements have been calculated in that respect.
Title: Re: Boyajians Star Updates And Discussion
Post by: RotoSequence on 05/28/2017 07:59 PM
Quote
Tabetha Boyajian @tsboyajian

Replying to @FaustoPerra and @lsu
Whatever is occulting the star is ~the size of the star itself. Or larger.

https://mobile.twitter.com/tsboyajian/status/868208793615822848

I want to understand that statement a bit better. If the largest dimming was 22%, and if the object is orbiting the star rather than in the interstellar medium hundreds of lightyears away from it, then why would it have to be the size of the star itself?

Would that not result in a 100% dimming, given that from our perspective the object is pretty much right on top of the star, rather than light years away from it?

Anything blocking KIC8462852's light while in orbit is going to be moving quickly relative to the star's position in the sky relative to the Earth. The longer the transit duration is, the larger the transiting object has to be. The cited percentages are only the peak quantities of light blocked, not the absolute size of the blocking objects.
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 05/28/2017 08:04 PM
Quote
Tabetha Boyajian @tsboyajian

Replying to @FaustoPerra and @lsu
Whatever is occulting the star is ~the size of the star itself. Or larger.

https://mobile.twitter.com/tsboyajian/status/868208793615822848

I want to understand that statement a bit better. If the largest dimming was 22%, and if the object is orbiting the star rather than in the interstellar medium hundreds of lightyears away from it, then why would it have to be the size of the star itself?

Would that not result in a 100% dimming, given that from our perspective the object is pretty much right on top of the star, rather than light years away from it?

Anything blocking KIC8462852's light while in orbit is going to be moving quickly relative to the star's position in the sky relative to the Earth. The longer the transit duration is, the larger the transiting object has to be. The cited percentages are only the peak quantities of light blocked, not the absolute size of the blocking objects.

Thanks.

So at the peak, if the object is the same size as the star, and if it is in direct line of sight between Earth and the star, would it not block close to 100% of the star's light? In other words, is the assumption that the object, at the peak dimming point, is perhaps not fully in our line of sight, meaning that only part of it is seen in the dimming event?
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/28/2017 08:05 PM
Quote
Tabetha Boyajian @tsboyajian

Replying to @FaustoPerra and @lsu
Whatever is occulting the star is ~the size of the star itself. Or larger.

https://mobile.twitter.com/tsboyajian/status/868208793615822848

I want to understand that statement a bit better. If the largest dimming was 22%, and if the object is orbiting the star rather than in the interstellar medium hundreds of lightyears away from it, then why would it have to be the size of the star itself?

Would that not result in a 100% dimming, given that from our perspective the object is pretty much right on top of the star, rather than light years away from it?

Anything blocking KIC8462852's light while in orbit is going to be moving quickly relative to the star's position in the sky relative to the Earth. The longer the transit duration is, the larger the transiting object has to be. The cited percentages are only the peak quantities of light blocked, not the absolute size of the blocking objects.

Thanks.

So at the peak, if the object is the same size as the star, and if it is in direct line of sight between Earth and the star, would it not block close to 100% of the star's light? In other words, is the assumption that the object, at the peak dimming point, is perhaps not fully in our line of sight, meaning that only part of it is seen in the dimming event?

That's how I read it.
Title: Re: Boyajians Star Updates And Discussion
Post by: RotoSequence on 05/28/2017 08:08 PM
Thanks.

So at the peak, if the object is the same size as the star, and if it is in direct line of sight between Earth and the star, would it not block close to 100% of the star's light? In other words, is the assumption that the object, at the peak dimming point, is perhaps not fully in our line of sight, meaning that only part of it is seen in the dimming event?

That's how I read it.

Likewise.
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 05/28/2017 08:14 PM
So at the peak, if the object is the same size as the star, and if it is in direct line of sight between Earth and the star, would it not block close to 100% of the star's light? In other words, is the assumption that the object, at the peak dimming point, is perhaps not fully in our line of sight, meaning that only part of it is seen in the dimming event?
There's no reason to assume it's 100% opaque. The question Dr.  Boyajian was answering was specifically about the megastructure idea. In that case, a swarm of moderately sized objects would be a lot easier to engineer, and would be a simpler fit to the observed behavior.

As rotosequence says, the size is inferred from the transit time, although this assumes a relatively close orbit i.e. the ~700 day period is the orbital period of the objects.
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 05/28/2017 08:20 PM
So at the peak, if the object is the same size as the star, and if it is in direct line of sight between Earth and the star, would it not block close to 100% of the star's light? In other words, is the assumption that the object, at the peak dimming point, is perhaps not fully in our line of sight, meaning that only part of it is seen in the dimming event?
There's no reason to assume it's 100% opaque. The question Dr.  Boyajian was answering was specifically about the megastructure idea. In that case, a swarm of moderately sized objects would be a lot easier to engineer, and would be a simpler fit to the observed behavior.

As rotosequence says, the size is inferred from the transit time, although this assumes a relatively close orbit i.e. the ~700 day period is the orbital period of the objects.

If I recall correctly, the latest event had a duration of about 5 days. Is that particularly long for an orbiting object? How long would a normal planetary transit dimming event last, from our 1400 light years distant perspective? Shorter than 5 days I presume?
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 05/28/2017 08:55 PM
So at the peak, if the object is the same size as the star, and if it is in direct line of sight between Earth and the star, would it not block close to 100% of the star's light? In other words, is the assumption that the object, at the peak dimming point, is perhaps not fully in our line of sight, meaning that only part of it is seen in the dimming event?
There's no reason to assume it's 100% opaque. The question Dr.  Boyajian was answering was specifically about the megastructure idea. In that case, a swarm of moderately sized objects would be a lot easier to engineer, and would be a simpler fit to the observed behavior.

As rotosequence says, the size is inferred from the transit time, although this assumes a relatively close orbit i.e. the ~700 day period is the orbital period of the objects.

If I recall correctly, the latest event had a duration of about 5 days. Is that particularly long for an orbiting object? How long would a normal planetary transit dimming event last, from our 1400 light years distant perspective? Shorter than 5 days I presume?

It depends on the size of the star and the distance the planet is orbiting from its star.  For a Jupiter-sized planet orbiting with a supposed 750 day period around 8462852 you would be looking at something like 23 hours.  That's pretty long as transits go, most of the time planets in the Kepler data are around a few hours.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/28/2017 09:06 PM
So at the peak, if the object is the same size as the star, and if it is in direct line of sight between Earth and the star, would it not block close to 100% of the star's light? In other words, is the assumption that the object, at the peak dimming point, is perhaps not fully in our line of sight, meaning that only part of it is seen in the dimming event?
There's no reason to assume it's 100% opaque. The question Dr.  Boyajian was answering was specifically about the megastructure idea. In that case, a swarm of moderately sized objects would be a lot easier to engineer, and would be a simpler fit to the observed behavior.

As rotosequence says, the size is inferred from the transit time, although this assumes a relatively close orbit i.e. the ~700 day period is the orbital period of the objects.

If I recall correctly, the latest event had a duration of about 5 days. Is that particularly long for an orbiting object? How long would a normal planetary transit dimming event last, from our 1400 light years distant perspective? Shorter than 5 days I presume?

It depends on the size of the star and the distance the planet is orbiting from its star.  For a Jupiter-sized planet orbiting with a supposed 750 day period around 8462852 you would be looking at something like 23 hours.  That's pretty long as transits go, most of the time planets in the Kepler data are around a few hours.

Do we know the very precise size of this star?
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 05/28/2017 09:17 PM
No, only nearby stars which have been monitored via interferometry are known with great precision, but it isn't going to make a huge difference to transit times unless it were an evolved giant, which it isn't. It is a main sequence F3 V star so the range of mass and radius is limited.
Title: Re: Boyajians Star Updates And Discussion
Post by: RotoSequence on 05/28/2017 09:27 PM
No, only nearby stars which have been monitored via interferometry are known with great precision, but it isn't going to make a huge difference to transit times unless it were an evolved giant, which it isn't. It is a main sequence F3 V star so the range of mass and radius is limited.

At the same time, Gaia's parallax measurements have lent some weight to the hypothesis that our measurements of the star are inaccurate due to increasing, long term extinction of the Star.
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 05/28/2017 09:42 PM
Not really, the Gaia TGAS results have large errors.  I wouldn't read too much into them until we have a full Gaia baseline.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/28/2017 09:45 PM
Not really, the Gaia TGAS results have large errors.  I wouldn't read too much into them until we have a full Gaia baseline.

That release has been put back to spring 2018 hasn't it?
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 05/28/2017 11:38 PM
I though the M dwarf was deemed as too distant and that it's recent movements have been calculated in that respect.
Do you have a reference for this? I would be surprised if we had much constraint on its actual motion, AFAIK the only thing we know is the angular separation. It took followup with Keck AO to even confirm as a distinct source from KIC 8462852, so we don't have long term knowledge of its motion.

From the original Boyajian et al paper (https://arxiv.org/abs/1509.03622):
Quote
Assuming the fainter star is associated with the main F-star target, and the two stars that are separated by ~ 1.95", they are ~ 885 AU apart. At this separation, the second star cannot currently be physically affecting the behavior of the Kepler target star, though could be affecting bodies in orbit around it via long term perturbations. If such a star is unbound from KIC 8462852, but traveling through the system perpendicular to our line of sight, it would take only 400 years to double its separation if traveling at 10 km/s. So, the passage would be relatively short-lived in astronomical terms.
Emphasis mine. The odds of catching an encounter like this in the act may be uncomfortably low, but if we did, it seems compatible with a pass close enough to cause significant effects.

The time for the effects of the encounter to reach the inner part of the system might be troublesome, but without constraints on the closest approach and distance along the line of site there's a fair bit of wiggle room.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 05/29/2017 05:29 AM
The distance of the M dwarf mostly just what Wright had tweeted in the past when asked about it.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 05/30/2017 01:25 PM
I though the M dwarf was deemed as too distant and that it's recent movements have been calculated in that respect.
Do you have a reference for this? I would be surprised if we had much constraint on its actual motion, AFAIK the only thing we know is the angular separation. It took followup with Keck AO to even confirm as a distinct source from KIC 8462852, so we don't have long term knowledge of its motion.

That's my understanding as well: we only know the angular separation.  The latest round of observations included both Kecks (and the LGS), so we may have got a new set of AO images.  If proper motion of the M dwarf is high enough, it may just be detectable.

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 05/31/2017 06:01 AM
Ballesteros et al posted an updated (still not reviewed / accepted) version of the Trojans pre-print discussed earlier https://arxiv.org/abs/1705.08427
Quote
Comments: 5 pages, 3 figures. v2: Corrected an error regarding the interpretation of the May 2017 event. Main conclusions unchanged. Revised version submitted to MNRAS Letters
The correction interprets the recent event as Hilda (https://en.wikipedia.org/wiki/Hilda_family) analogs rather than a secondary eclipse. Seems a bit contrived, but I guess if you are willing to accept enough trojans to cause a ~20% dip...
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/05/2017 05:56 PM
Tabby has updated her blog.

http://www.wherestheflux.com/single-post/2017/06/04/Dip-update-7n
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 06/14/2017 05:57 AM
Apparently, KIC 8462852 might be dipping again.

Reported by Ben Montet on Twitter, citing observations by Bruce Gary.

https://twitter.com/benmontet/status/874748832357261313
http://www.brucegary.net/KIC846/#2017.06.13_V

Not heard any LCOGT confirmation yet.

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 06/14/2017 08:18 AM
Notice the timing between this dip and the one in May. It's very close to the spacing of the complex of dips centred around D1540 in the Kepler data.  A coincidence or more evidence this is in orbit?
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/14/2017 08:27 AM
Notice the timing between this dip and the one in May. It's very close to the spacing of the complex of dips centred around D1540 in the Kepler data.  A coincidence or more evidence this is in orbit?

Someone on the relevant Reddit appears to have predicted this. It may indicate something in a 24.2 day orbit of the star.

https://www.reddit.com/r/KIC8462852/comments/6h3655/a_new_dip_has_started_now_at_10/
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 06/14/2017 08:56 AM
If it were a 24 day orbit we would see them every* 24 days.  There would also be IR excess.

I was thinking perhaps multiple objects on roughly the same ~750d eccentric orbit that happen to cross our line of sight ~24d apart.





*well there are edge cases, but doubtful here.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/14/2017 09:30 AM
According to what I've read on the same Reddit Tabby has confirmed a shallow dip. I should add I can't see anything about it on either her or Jason's Twitter feed.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/14/2017 09:32 AM
If it were a 24 day orbit we would see them every* 24 days.  There would also be IR excess.

I was thinking perhaps multiple objects on roughly the same ~750d eccentric orbit that happen to cross our line of sight ~24d apart.





*well there are edge cases, but doubtful here.

Yes you're right as that's been disputed in the same thread with mention of that 750 day orbit.

I believe someone else indicated with this that on the 17th July it should go into a major dip.
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 06/14/2017 10:39 AM
Having said that, remember the spurious 48.4 day period from the original paper?  Well some of the shallower dips earlier on in the lightcurve that are usually glossed over fit cycles of 24.2 days.

The duration between the 22% dip at D1519.6 and dip 1 and 2 in the original paper is 57 or 52 ~24.2 day cycles respectively.  The duration between the other large dip near the end of the Kepler data at D1568.5 and these earlier dips is 59 or 54 cycles respectively.



Interesting aside, perhaps the 750 day period is spurious and that the shallower events are secondary eclipses?
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/14/2017 11:15 AM
Having said that, remember the spurious 48.4 day period from the original paper?  Well some of the shallower dips earlier on in the lightcurve that are usually glossed over fit cycles of 24.2 days.

The duration between the 22% dip at D1519.6 and dip 1 and 2 in the original paper is 57 or 52 ~24.2 day cycles respectively.  The duration between the other large dip near the end of the Kepler data at D1568.5 and these earlier dips is 59 or 54 cycles respectively.



Interesting aside, perhaps the 750 day period is spurious and that the shallower events are secondary eclipses?

Probably stating the very obvious here but probably what all observers need is one of the big dips, so that it clearly shows against the noise and error bars.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/14/2017 11:23 AM
I believe some indicated with this that on the 17th July it should go into a major dip.

Well, there we are. A line in the sand!

Can someone verify this date?
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 06/15/2017 06:00 AM
Still dipping ... apparently still ~1% down.

https://twitter.com/brettmor/status/875224630666993664

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/15/2017 07:00 AM
Still dipping ... apparently still ~1% down.

https://twitter.com/brettmor/status/875224630666993664

--- Tony
Some confusing and contradictory data on the Reddit thread.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 06/15/2017 07:11 AM
Some confusing and contradictory data on the Reddit thread.

I'm not too worried by that Reddit. First, detecting a 1% dip is beyond the capabilities of many on AAVSO (if nothing else because most don't have a continuous set of observations). Second, there are some pretty wild and unsubstantiated claims there ...

I'll go with the people with access to large instruments :-)

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/15/2017 07:25 AM
Some confusing and contradictory data on the Reddit thread.

I'm not too worried by that Reddit. First, detecting a 1% dip is beyond the capabilities of many on AAVSO (if nothing else because most don't have a continuous set of observations). Second, there are some pretty wild and unsubstantiated claims there ...

I'll go with the people with access to large instruments :-)

--- Tony

Brett Morris Twitter.

https://mobile.twitter.com/brettmor/status/875243485661609985
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/15/2017 09:26 AM
Quote
Update from Bruce:

Preliminary result for Jun 15 (after 1.7 hrs). The fade feature that began a couple days ago is slowly recovering.

KIC 8462852 Daily Normalized Flux, 2017 May 02 - Jun 15 - v7615

http://www.brucegary.net/KIC846/17.06.15%20KIC846%28V%29%20d7615%20May01-50%20Daily%20NFL%2005.jpg
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/15/2017 07:36 PM
Here is a graph of the 11th June event from TRAPPIST-1 via Tabby.

https://drive.google.com/file/d/0B_LvagsQCx-cZHhDMVYyMDdpR2s/view

Also this.

Quote
Paul Thompson @trailrunnerlife

@Astro_Wright any update on when we might expect publication of GBT obs for Tabby's Star? Lots of hungry data scientists...
8:22 pm · 15 Jun 2017

Jason Wright @Astro_Wright
·
8m

Replying to @trailrunnerlife
It turns out transferring and collecting and organizing 610TB of data on a brand-new data center takes time! Much longer than I had hoped.

Jason Wright @Astro_Wright
·
7m

We're making slow progress.  We do hope to make snippets freely downloadable so others can chew on it and suggest analyses for us to run!

Paul Thompson @trailrunnerlife
·
4m

that's great news, thanks!

https://mobile.twitter.com/trailrunnerlife/status/875433474433437697
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/16/2017 06:43 AM
Tabby's latest blog posting.

http://www.wherestheflux.com/single-post/2017/06/15/Dip-update-9n

According to Bruce, the latest dip is now almost down to 2% again!

http://www.brucegary.net/KIC846/
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/16/2017 11:57 AM
Can anyone confirm the following statement as seen via Reddit?

Quote
Take note too that just before the start of the Kepler 1568 8% dip, there was a spike in brightness. In fact, it was the single brightest plots across the entire 4 years of Kepler data. We also observed this brightening between May 7 - 9. As if we were seeing a reflection of something before crossing our line of sight.
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 06/16/2017 12:20 PM
Not present in the SAP flux.  It is created by the Pre-search Data Conditioning algorithm's attempts to smooth the curve while retaining the high frequency signal (the surrounding dips).
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/16/2017 12:54 PM
Not present in the SAP flux.  It is created by the Pre-search Data Conditioning algorithm's attempts to smooth the curve while retaining the high frequency signal (the surrounding dips).

Thank you for the clarification.

I am assuming it's a necessary evil as it sounds it might be?
Title: Re: Boyajians Star Updates And Discussion
Post by: JasonAW3 on 06/16/2017 01:21 PM
Thanks.

So at the peak, if the object is the same size as the star, and if it is in direct line of sight between Earth and the star, would it not block close to 100% of the star's light? In other words, is the assumption that the object, at the peak dimming point, is perhaps not fully in our line of sight, meaning that only part of it is seen in the dimming event?

That's how I read it.


Likewise.

Either that or a non-solid object consisting of debris or gases.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/16/2017 01:24 PM
Thanks.

So at the peak, if the object is the same size as the star, and if it is in direct line of sight between Earth and the star, would it not block close to 100% of the star's light? In other words, is the assumption that the object, at the peak dimming point, is perhaps not fully in our line of sight, meaning that only part of it is seen in the dimming event?

That's how I read it.


Likewise.

Either that or a non-solid object consisting of debris or gases.

I'd of thought strict periodicity if confirmed would make that less likely.
Title: Re: Boyajians Star Updates And Discussion
Post by: JasonAW3 on 06/16/2017 01:49 PM
Ok, maybe I missed the answers to the following questions, but I think they may be something that may need to be pondered.

     First; if Tabby's Star is approximately 1.43 times the size of our sun, but is an F3V star, wouldn't a 700 day orbit put whatever this object is, be in what should be approximately, the "Goldilocks Zone"?

     Second; if we're seeing this "object" every 700 days, shouldn't we be able to calculate the approximate mass by the actual wobble of the star?  If this is some sort of dispersed object, or collection of objects, it would slow the actual wobble to a flatter curve, but should still be able to be parsed out of the data.

     Third; if whatever this object is made of has a certain amount of reflectivity, shouldn't there be a spike in luminosity, of some kind, approximately 350 days after the beginning of the major dip in luminosity?

      Like I said, these are likely questions answered earlier in the thread, but I'd appreciate any links someone could provide to the answers to these questions.  Not being lazy, but I am at work and don't want to spend too much time on this while working.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/16/2017 02:04 PM
Ok, maybe I missed the answers to the following questions, but I think they may be something that may need to be pondered.

     First; if Tabby's Star is approximately 1.43 times the size of our sun, but is an F3V star, wouldn't a 700 day orbit put whatever this object is, be in what should be approximately, the "Goldilocks Zone"?

     Second; if we're seeing this "object" every 700 days, shouldn't we be able to calculate the approximate mass by the actual wobble of the star?  If this is some sort of dispersed object, or collection of objects, it would slow the actual wobble to a flatter curve, but should still be able to be parsed out of the data.

     Third; if whatever this object is made of has a certain amount of reflectivity, shouldn't there be a spike in luminosity, of some kind, approximately 350 days after the beginning of the major dip in luminosity?

      Like I said, these are likely questions answered earlier in the thread, but I'd appreciate any links someone could provide to the answers to these questions.  Not being lazy, but I am at work and don't want to spend too much time on this while working.

I would also add that there appears to be something in the idea of a 24.2 day cycle.
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 06/16/2017 02:33 PM
Not present in the SAP flux.  It is created by the Pre-search Data Conditioning algorithm's attempts to smooth the curve while retaining the high frequency signal (the surrounding dips).

Thank you for the clarification.

I am assuming it's a necessary evil as it sounds it might be?

Pretty much; the automated regression fitting does its best to mask out the dips to preserve them, but it's not going to be perfect and fitting with some of the dipped data leads to the surrounding areas being distorted.

Ok, maybe I missed the answers to the following questions, but I think they may be something that may need to be pondered.

     First; if Tabby's Star is approximately 1.43 times the size of our sun, but is an F3V star, wouldn't a 700 day orbit put whatever this object is, be in what should be approximately, the "Goldilocks Zone"?

     Second; if we're seeing this "object" every 700 days, shouldn't we be able to calculate the approximate mass by the actual wobble of the star?  If this is some sort of dispersed object, or collection of objects, it would slow the actual wobble to a flatter curve, but should still be able to be parsed out of the data.

     Third; if whatever this object is made of has a certain amount of reflectivity, shouldn't there be a spike in luminosity, of some kind, approximately 350 days after the beginning of the major dip in luminosity?

      Like I said, these are likely questions answered earlier in the thread, but I'd appreciate any links someone could provide to the answers to these questions.  Not being lazy, but I am at work and don't want to spend too much time on this while working.

1.  Yes if on a circular orbit a ~750 day period (still a big if) would be roughly in the HZ. However to explain the lack of IR excess then the object would presumably have to be on a highly eccentric comet-like orbit.  So in fact it would only pass through the habitable zone for a part of the orbit and then be deep-fried for the rest of it.

2. Radial velocity measurements have been conducted on this star which found no signal.  However as it's not the easiest of targets for radial velocity searches this has only rules out objects the mass of a small star and above very close-by.

3.  Trouble is Kepler is not designed to do that kind of study, it is not good at accurately measuring the absolute brightness over long periods.  This is why Montet and Simon used the full frame images, essentially engineering data, to find the star has been dimming over the four-year mission.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/16/2017 02:37 PM
Not present in the SAP flux.  It is created by the Pre-search Data Conditioning algorithm's attempts to smooth the curve while retaining the high frequency signal (the surrounding dips).

Thank you for the clarification.

I am assuming it's a necessary evil as it sounds it might be?

Pretty much; the automated regression fitting does its best to mask out the dips to preserve them, but it's not going to be perfect and fitting with some of the dipped data leads to the surrounding areas being distorted.

Ok, maybe I missed the answers to the following questions, but I think they may be something that may need to be pondered.

     First; if Tabby's Star is approximately 1.43 times the size of our sun, but is an F3V star, wouldn't a 700 day orbit put whatever this object is, be in what should be approximately, the "Goldilocks Zone"?

     Second; if we're seeing this "object" every 700 days, shouldn't we be able to calculate the approximate mass by the actual wobble of the star?  If this is some sort of dispersed object, or collection of objects, it would slow the actual wobble to a flatter curve, but should still be able to be parsed out of the data.

     Third; if whatever this object is made of has a certain amount of reflectivity, shouldn't there be a spike in luminosity, of some kind, approximately 350 days after the beginning of the major dip in luminosity?

      Like I said, these are likely questions answered earlier in the thread, but I'd appreciate any links someone could provide to the answers to these questions.  Not being lazy, but I am at work and don't want to spend too much time on this while working.

1.  Yes if on a circular orbit a ~750 day period (still a big if) would be roughly in the HZ. However to explain the lack of IR excess then the object would presumably have to be on a highly eccentric comet-like orbit.  So in fact it would only pass through the habitable zone for a part of the orbit and then be deep-fried for the rest of it.

2. Radial velocity measurements have been conducted on this star which found no signal.  However as it's not the easiest of targets for radial velocity searches this has only rules out objects the mass of a small star and above very close-by.

3.  Trouble is Kepler is not designed to do that kind of study, it is not good at accurately measuring the absolute brightness over long periods.  This is why Montet and Simon used the full frame images, essentially engineering data, to find the star has been dimming over the four-year mission.

What's your current thinking now on the 24.2 cycle?

Also I hope we get a 8% dip as we really need a clear signal to look at above the noise.
Title: Re: Boyajians Star Updates And Discussion
Post by: JasonAW3 on 06/16/2017 02:46 PM
Ok, maybe I missed the answers to the following questions, but I think they may be something that may need to be pondered.

     First; if Tabby's Star is approximately 1.43 times the size of our sun, but is an F3V star, wouldn't a 700 day orbit put whatever this object is, be in what should be approximately, the "Goldilocks Zone"?

     Second; if we're seeing this "object" every 700 days, shouldn't we be able to calculate the approximate mass by the actual wobble of the star?  If this is some sort of dispersed object, or collection of objects, it would slow the actual wobble to a flatter curve, but should still be able to be parsed out of the data.

     Third; if whatever this object is made of has a certain amount of reflectivity, shouldn't there be a spike in luminosity, of some kind, approximately 350 days after the beginning of the major dip in luminosity?

      Like I said, these are likely questions answered earlier in the thread, but I'd appreciate any links someone could provide to the answers to these questions.  Not being lazy, but I am at work and don't want to spend too much time on this while working.

I would also add that there appears to be something in the idea of a 24.2 day cycle.

If this is true, it's likely a separate object.  Kind of like a tight orbiting Super Earth sized Mercury like object.

      But this does bring up an interesting point; if this 24.2 day fluctuation IS a Super Earth sized object, if it has a similar mass to what a solid body of that scale should have, then it should induce a fairly measurable wobble.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/16/2017 02:49 PM
Ok, maybe I missed the answers to the following questions, but I think they may be something that may need to be pondered.

     First; if Tabby's Star is approximately 1.43 times the size of our sun, but is an F3V star, wouldn't a 700 day orbit put whatever this object is, be in what should be approximately, the "Goldilocks Zone"?

     Second; if we're seeing this "object" every 700 days, shouldn't we be able to calculate the approximate mass by the actual wobble of the star?  If this is some sort of dispersed object, or collection of objects, it would slow the actual wobble to a flatter curve, but should still be able to be parsed out of the data.

     Third; if whatever this object is made of has a certain amount of reflectivity, shouldn't there be a spike in luminosity, of some kind, approximately 350 days after the beginning of the major dip in luminosity?

      Like I said, these are likely questions answered earlier in the thread, but I'd appreciate any links someone could provide to the answers to these questions.  Not being lazy, but I am at work and don't want to spend too much time on this while working.

I would also add that there appears to be something in the idea of a 24.2 day cycle.

If this is true, it's likely a separate object.  Kind of like a tight orbiting Super Earth sized Mercury like object.

      But this does bring up an interesting point; if this 24.2 day fluctuation IS a Super Earth sized object, if it has a similar mass to what a solid body of that scale should have, then it should induce a fairly measurable wobble.

Is the star's larger size that makes measuring wobbles in it difficult or is it just the sheer distance or a combination of the two?
Title: Re: Boyajians Star Updates And Discussion
Post by: jgoldader on 06/16/2017 03:37 PM

Is the star's larger size that makes measuring wobbles in it difficult or is it just the sheer distance or a combination of the two?

KIC 8462852 is about V~11.7 mag, so it would look to be within the reach of the spectrometers used to find planets, though on the faint end.  The spectroscopy is very high resolution, so you just run out of flux with faint stars.  The data analysis is non-trivial; as I recall, you're looking for correlations, a statistical signal, of differences between the observed and laboratory (rest-frame) wavelengths of many, many spectral absorption lines.  If your spectrum is faint, the S/N just doesn't support the analysis.

I'm wondering if the spectral type is an issue.  The spectroscopic technique used to measure radial velocity variations requires lots of absorption lines, which are stronger in cooler stars, yet KIC is hotter than the Sun.  I flipped through Wikipedia's list of exoplanets, and the great majority are around G/K stars, with very few F's.  The M's are not well represented in the list.  I'd guess part of this is due to the very low M luminosities, meaning most are just too faint to study, but they also apparently tend to be discounted due to their low masses implying low likelihood of finding massive planets (though there are of course important counterexamples, such as the Trappist planets).  So maybe there aren't enough strong metal lines in the F star to work.

All that said, I'd be surprised if nobody's looking, but maybe they're just being quiet about it.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/16/2017 03:51 PM

Is the star's larger size that makes measuring wobbles in it difficult or is it just the sheer distance or a combination of the two?

KIC 8462852 is about V~11.7 mag, so it would look to be within the reach of the spectrometers used to find planets, though on the faint end.  The spectroscopy is very high resolution, so you just run out of flux with faint stars.  The data analysis is non-trivial; as I recall, you're looking for correlations, a statistical signal, of differences between the observed and laboratory (rest-frame) wavelengths of many, many spectral absorption lines.  If your spectrum is faint, the S/N just doesn't support the analysis.

I'm wondering if the spectral type is an issue.  The spectroscopic technique used to measure radial velocity variations requires lots of absorption lines, which are stronger in cooler stars, yet KIC is hotter than the Sun.  I flipped through Wikipedia's list of exoplanets, and the great majority are around G/K stars, with very few F's.  The M's are not well represented in the list.  I'd guess part of this is due to the very low M luminosities, meaning most are just too faint to study, but they also apparently tend to be discounted due to their low masses implying low likelihood of finding massive planets (though there are of course important counterexamples, such as the Trappist planets).  So maybe there aren't enough strong metal lines in the F star to work.

All that said, I'd be surprised if nobody's looking, but maybe they're just being quiet about it.

What are F stars thought of in general for habitability they have got to be better bets than M dwarfs I would have thought?

I looked into this but couldn't find much though I see we have examples that host planets.
Title: Re: Boyajians Star Updates And Discussion
Post by: leovinus on 06/16/2017 04:27 PM

Is the star's larger size that makes measuring wobbles in it difficult or is it just the sheer distance or a combination of the two?

KIC 8462852 is about V~11.7 mag, so it would look to be within the reach of the spectrometers used to find planets, though on the faint end.  The spectroscopy is very high resolution, so you just run out of flux with faint stars.  The data analysis is non-trivial; as I recall, you're looking for correlations, a statistical signal, of differences between the observed and laboratory (rest-frame) wavelengths of many, many spectral absorption lines.  If your spectrum is faint, the S/N just doesn't support the analysis.

I'm wondering if the spectral type is an issue.  The spectroscopic technique used to measure radial velocity variations requires lots of absorption lines, which are stronger in cooler stars, yet KIC is hotter than the Sun.  I flipped through Wikipedia's list of exoplanets, and the great majority are around G/K stars, with very few F's.  The M's are not well represented in the list.  I'd guess part of this is due to the very low M luminosities, meaning most are just too faint to study, but they also apparently tend to be discounted due to their low masses implying low likelihood of finding massive planets (though there are of course important counterexamples, such as the Trappist planets).  So maybe there aren't enough strong metal lines in the F star to work.

All that said, I'd be surprised if nobody's looking, but maybe they're just being quiet about it.

What are F stars thought of in general for habitability they have got to be better bets than M dwarfs I would have thought?

I looked into this but couldn't find much though I see we have examples that host planets.

Our sun is a G2, the sequence of stars in terms of temperature is O B A F G K M (from hot to cool) i.e. F is a bit hotter than our sun. As far as I know, the difference between F and G is not very extreme and I would think that F stars in principle should be ok for hospitable planets.
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 06/16/2017 07:15 PM

Is the star's larger size that makes measuring wobbles in it difficult or is it just the sheer distance or a combination of the two?

KIC 8462852 is about V~11.7 mag, so it would look to be within the reach of the spectrometers used to find planets, though on the faint end.  The spectroscopy is very high resolution, so you just run out of flux with faint stars.  The data analysis is non-trivial; as I recall, you're looking for correlations, a statistical signal, of differences between the observed and laboratory (rest-frame) wavelengths of many, many spectral absorption lines.  If your spectrum is faint, the S/N just doesn't support the analysis.

I'm wondering if the spectral type is an issue.  The spectroscopic technique used to measure radial velocity variations requires lots of absorption lines, which are stronger in cooler stars, yet KIC is hotter than the Sun.  I flipped through Wikipedia's list of exoplanets, and the great majority are around G/K stars, with very few F's.  The M's are not well represented in the list.  I'd guess part of this is due to the very low M luminosities, meaning most are just too faint to study, but they also apparently tend to be discounted due to their low masses implying low likelihood of finding massive planets (though there are of course important counterexamples, such as the Trappist planets).  So maybe there aren't enough strong metal lines in the F star to work.

All that said, I'd be surprised if nobody's looking, but maybe they're just being quiet about it.

The problem with early-type F stars like KIC 8462852 is they lack any substantial convective layer which means little intrinsic magnetic dynamo. With no magnetic dynamo there is no magnetic braking to slow the star's rotation.  The rapid rotation smears out most of the absorption lines beyond recognition, which is why they have so few clear lines.  That affects how accurate a radial velocity measurement is going to be.  Of course their greater mass also doesn't help as the pull caused by a planet is naturally smaller.

The reason for the lack of M dwarfs is them being faint, but also that they are the most magnetically active stars due to being fully convective.  As a result of the magnetic activity they have considerable spotting, which mimics a change in the star's radial velocity (or indeed transits). So much so you can tell most M-dwarfs in the Kepler data within in a second of looking at the lightcurve because they are so characteristically bouncy which is caused by sunspot regions moving around.   There are far easier targets when you consider radial velocity searches are very time-consuming.

As for habitability F stars aren't considered any worse than Gs to my knowledge, though i can't remember seeing much written on the subject.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/16/2017 07:18 PM

Is the star's larger size that makes measuring wobbles in it difficult or is it just the sheer distance or a combination of the two?

KIC 8462852 is about V~11.7 mag, so it would look to be within the reach of the spectrometers used to find planets, though on the faint end.  The spectroscopy is very high resolution, so you just run out of flux with faint stars.  The data analysis is non-trivial; as I recall, you're looking for correlations, a statistical signal, of differences between the observed and laboratory (rest-frame) wavelengths of many, many spectral absorption lines.  If your spectrum is faint, the S/N just doesn't support the analysis.

I'm wondering if the spectral type is an issue.  The spectroscopic technique used to measure radial velocity variations requires lots of absorption lines, which are stronger in cooler stars, yet KIC is hotter than the Sun.  I flipped through Wikipedia's list of exoplanets, and the great majority are around G/K stars, with very few F's.  The M's are not well represented in the list.  I'd guess part of this is due to the very low M luminosities, meaning most are just too faint to study, but they also apparently tend to be discounted due to their low masses implying low likelihood of finding massive planets (though there are of course important counterexamples, such as the Trappist planets).  So maybe there aren't enough strong metal lines in the F star to work.

All that said, I'd be surprised if nobody's looking, but maybe they're just being quiet about it.

The problem with early-type F stars like KIC 8462852 is they lack any substantial convective layer which means little intrinsic magnetic dynamo. With no magnetic dynamo there is no magnetic braking slowing the star's rotation.  The rapid rotation smears out most of the absorption lines beyond recognition, which is why they have so few clear lines.  That affects how accurate a radial velocity measurement is going to be.  Of course their greater mass also doesn't help as the pull caused by a planet is naturally smaller.

The reason for the lack of M dwarfs is them being faint, but also that they are the most magnetically active stars due to being fully convective.  As a result of the magnetic activity they have considerable spotting, which mimics a change in the star's radial velocity (or indeed transits). So much so you can tell most M-dwarfs in the Kepler data within in a second of looking at the lightcurve because they are so bouncy which is caused by sunspot regions moving around.   There are far easier targets when you consider radial velocity searches are very time-consuming.

As for habitability F stars aren't considered any worse than Gs to my knowledge.

That's interesting info you've got and more than Wikipedia has on them.

By the way the dip is ongoing.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/16/2017 10:22 PM
Tabby is looking for people to observe it tonight.

Quote
Tabetha Boyajian @tsboyajian

#TabbysStar is approaching 2% dim - WHO WILL OBSERVE TONIGHT?!!

https://mobile.twitter.com/tsboyajian/status/875839712682020864
Title: Re: Boyajians Star Updates And Discussion
Post by: Orbiter on 06/16/2017 10:26 PM
I'm wondering how much of a dip would be significant enough to observe with the naked eye. Obviously a 2% dimming won't be enough. I have experience observing eclipsing binaries with an 8" telescope and Tabby's star apparently has dimmed as much as >20% in the past. 
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/17/2017 08:38 AM
Even with our best telescopes it would just be one point of light amongst many others.
Title: Re: Boyajians Star Updates And Discussion
Post by: AncientU on 06/17/2017 05:05 PM
I'm wondering how much of a dip would be significant enough to observe with the naked eye. Obviously a 2% dimming won't be enough. I have experience observing eclipsing binaries with an 8" telescope and Tabby's star apparently has dimmed as much as >20% in the past.

Naked eye stars go down to about 5th or 6th magnitude, so Tabby's star (11th magnitude) would be >100x too faint for naked eye viewing.  A 20% dip of a faint star at edge of naked eye viewing would not be perceptible anyway -- the eye can discriminate about 1 magnitude, which goes back to the origins of the magnitude scale.  Large telescopes image stars to 24-25th mags (LSST survey, for instance gets down to 24.5 or so with two 15 sec observations).  Same telescope with longer integrations can obviously go fainter than this by several magnitudes.

Cool stars like M-Dwarfs are excellent planet hosts with the most elaborate planetary systems yet seen.  They do have active surfaces, so are challenging to do radial velocity searches -- also they are faint objects and most flux is longward of (redder than) optical, so near-infrared instruments are needed for RV work.  Kepler, which uses transit spectroscopy, found several wonderful systems around early (bluer) M-Dwarfs.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/17/2017 10:29 PM
Latest blog post from Tabby and the star is still dipping further.

http://www.wherestheflux.com/single-post/2017/06/17/Dip-update-11n---dip-2-is-still-dipping
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 06/18/2017 04:22 AM
Latest update for 6/17.   Watch to the end to see how the latest dimming possibly coincides with past dimming measured by Kepler.

https://www.youtube.com/watch?v=gZYyeh9aMWE
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/18/2017 07:30 PM
Interesting conversation involving Ben Montet on Twitter.

https://mobile.twitter.com/benmontet/status/876331722295713792
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/18/2017 09:37 PM
If it follows the sequence we should next see a dip to 8% and over a number of days a return to nominal.
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 06/18/2017 09:46 PM
If it follows the sequence we should next see a dip to 8% and over a number of days a return to nominal.

If we are indeed seeing the prelude to the previous large 8% drop, then what the heck happened to the 22% drop that should have preceded it by a month or thereabouts? Half the world was watching it during this period (a slight overstatement for dramatic effect). Did they just miss it?
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/18/2017 09:48 PM
If it follows the sequence we should next see a dip to 8% and over a number of days a return to nominal.

If we are indeed seeing the prelude to the previous large 8% drop, then what the heck happened to the 22% drop that should have preceded it by a couple of months or thereabouts? Half the world was watching it during this period (a slight overstatement for dramatic effect). Did they just miss it?

I thought that might be explained by it being hard to observe at that time, wasn't it badly placed in the sky for observation?
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 06/18/2017 09:58 PM
If it follows the sequence we should next see a dip to 8% and over a number of days a return to nominal.

If we are indeed seeing the prelude to the previous large 8% drop, then what the heck happened to the 22% drop that should have preceded it by a couple of months or thereabouts? Half the world was watching it during this period (a slight overstatement for dramatic effect). Did they just miss it?

I thought that might be explained by it being hard to observe at that time, wasn't it badly placed in the sky for observation?

Ok. I wasn't aware of that. Are you aware of the speculation about the various dips being multiples of one another, basically hypothesizing a number of fixed configuration swarms that sometimes overlap and sometimes don't in our line of sight, leading to different sized dips depending on where they are in their individual orbits?

In which case the big 22% dip would represent a number of these swarms happening to appear next to each other in our line of sight, to cumulatively block out a massive 22% of the star's light. This alignment might not occur at a set frequency, or even to exactly the same extent again, if the individual swarms are in different orbits. Perhaps not even on the same orbital plane and we just happen to catch whichever bits of each swarm happen to cross our line of sight at any given point in time.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/18/2017 10:04 PM
If it follows the sequence we should next see a dip to 8% and over a number of days a return to nominal.

If we are indeed seeing the prelude to the previous large 8% drop, then what the heck happened to the 22% drop that should have preceded it by a couple of months or thereabouts? Half the world was watching it during this period (a slight overstatement for dramatic effect). Did they just miss it?

I thought that might be explained by it being hard to observe at that time, wasn't it badly placed in the sky for observation?

Ok. I wasn't aware of that. Are you aware of the speculation about the various dips being multiples of one another, basically hypothesizing a number of fixed configuration swarms that sometimes overlap and sometimes don't, in our line of sight, leading to different sized dips depending on where they are in their individual orbits?

In which case the big 22% dip would represent a number of these swarms happening to appear next to each other in our line of sight, to cumulatively block out a massive 22% of the star's light. This alignment might not occur at a set frequency, or even to exactly the same extent again, if the individual swarms are in different orbits. Perhaps not even on the same orbital plane and we just happen to catch whichever bits of each swarm happwn to cross our line of sight at any given point in time.

I think it's dangerous to speculate numerically myself. The thing that bothers me is if for the sake of wild speculation it was an ETI why would we expect to find a pattern we'd recognise?

By the way have you see that Astrophysicist and  Sci Fi author Gregory Benford has stated on FB: "Fits no good model. A real mystery." (Via Reddit)
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 06/18/2017 10:13 PM
If it follows the sequence we should next see a dip to 8% and over a number of days a return to nominal.

If we are indeed seeing the prelude to the previous large 8% drop, then what the heck happened to the 22% drop that should have preceded it by a couple of months or thereabouts? Half the world was watching it during this period (a slight overstatement for dramatic effect). Did they just miss it?

I thought that might be explained by it being hard to observe at that time, wasn't it badly placed in the sky for observation?

Ok. I wasn't aware of that. Are you aware of the speculation about the various dips being multiples of one another, basically hypothesizing a number of fixed configuration swarms that sometimes overlap and sometimes don't, in our line of sight, leading to different sized dips depending on where they are in their individual orbits?

In which case the big 22% dip would represent a number of these swarms happening to appear next to each other in our line of sight, to cumulatively block out a massive 22% of the star's light. This alignment might not occur at a set frequency, or even to exactly the same extent again, if the individual swarms are in different orbits. Perhaps not even on the same orbital plane and we just happen to catch whichever bits of each swarm happwn to cross our line of sight at any given point in time.

I think it's dangerous to speculate numerically myself. The thing that bothers me is if for the sake of wild speculation it was an ETI why would we expect to find a pattern we'd recognise?

By the way have you see that Astrophysicist and  Sci Fi author Gregory Benford has stated on FB: "Fits no good model. A real mystery."

Not sure what you mean by a recognizeable pattern. I'm not suggesting the pattern is deliberate. We would simply be observing whichever such objects coincidentally crossed our line of sight.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/18/2017 10:15 PM
If it follows the sequence we should next see a dip to 8% and over a number of days a return to nominal.

If we are indeed seeing the prelude to the previous large 8% drop, then what the heck happened to the 22% drop that should have preceded it by a couple of months or thereabouts? Half the world was watching it during this period (a slight overstatement for dramatic effect). Did they just miss it?

I thought that might be explained by it being hard to observe at that time, wasn't it badly placed in the sky for observation?

Ok. I wasn't aware of that. Are you aware of the speculation about the various dips being multiples of one another, basically hypothesizing a number of fixed configuration swarms that sometimes overlap and sometimes don't, in our line of sight, leading to different sized dips depending on where they are in their individual orbits?

In which case the big 22% dip would represent a number of these swarms happening to appear next to each other in our line of sight, to cumulatively block out a massive 22% of the star's light. This alignment might not occur at a set frequency, or even to exactly the same extent again, if the individual swarms are in different orbits. Perhaps not even on the same orbital plane and we just happen to catch whichever bits of each swarm happwn to cross our line of sight at any given point in time.

I think it's dangerous to speculate numerically myself. The thing that bothers me is if for the sake of wild speculation it was an ETI why would we expect to find a pattern we'd recognise?

By the way have you see that Astrophysicist and  Sci Fi author Gregory Benford has stated on FB: "Fits no good model. A real mystery."

Not sure what you mean by a recognizeable pattern. I'm not suggesting the pattern is deliberate. We would simply be observing whichever such objects coincidentally crossed our line of sight.

Yeah sorry I should of been clearer. Put it down to being infuriated by people posting online thinking little green men are sending us numerical signals. (I kid not).
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 06/18/2017 10:26 PM

Yeah sorry I should of been clearer. Put it down to being infuriated by people posting online thinking little green men are sending us numerical signals. (I kid not).

Ah, ok. No, nothing like that. Just objects in different orbits, aligning at times, and not at other times. From our vantage point.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/18/2017 10:32 PM

Yeah sorry I should of been clearer. Put it down to being infuriated by people posting online thinking little green men are sending us numerical signals. (I kid not).

Ah, ok. No, nothing like that. Just objects in different orbits, aligning at times, and not at other times. From our vantage point.

I don't think we are going to easily solve this star though if it does have strict repeats and periodicity that may give us clues. If nothing else for now it shows Kepler produced good data for it which refutes the claims of certain people who were not just casting doubt on it but the teams behind it.
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 06/19/2017 12:25 AM

Yeah sorry I should of been clearer. Put it down to being infuriated by people posting online thinking little green men are sending us numerical signals. (I kid not).

Ah, ok. No, nothing like that. Just objects in different orbits, aligning at times, and not at other times. From our vantage point.


I don't think we are going to easily solve this star though if it does have strict repeats and periodicity that may give us clues. If nothing else for now it shows Kepler produced good data for it which refutes the claims of certain people who were not just casting doubt on it but the teams behind it.


Repeats in periodicity, that also match the same shape & optical depth as previous dips is going to be very hard to explain with comets, torn up planets, & various transient phenomena.  Same goes for mechanism internal to the star.   Seems very unlikely that they would repeat.  So I guess it will be interesting to see what happens in the next 20-30 days.

As to refutation of the person proposing problems with the Kepler instruments, if we are talking about the one frequenting these NSF threads, that person's objections were never rooted in anything factual, and contained nothing of merit that called for any rebuttal.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/19/2017 04:00 AM
This video contains the latest Bruce Gary data for the 18th June.

https://m.youtube.com/watch?v=U30v_jlk3GY
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/19/2017 08:14 PM
Tabby's latest update. Seems the weather got in the way here.

http://www.wherestheflux.com/single-post/2017/06/19/Dip-update-12n---dip-2-still-dipping-but-not-as-much
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/20/2017 07:24 AM
This video contains the latest Bruce Gary data for the 19th June.

https://www.youtube.com/watch?v=7bpX586amf0
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/20/2017 07:29 AM
Speculation is that the current dip is like the d1540 dip in the Kepler data not d1568 as was initially thought. Meaning we should get the 8% dip next month if there is indeed a repeating pattern.
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 06/20/2017 07:52 AM
Speculation is that the current dip is like the d1540 dip in the Kepler data not d1568 as was initially thought. Meaning we should get the 8% dip next month if there is indeed a repeating pattern.

Star One

You seem to have followed the discussion about this star quite closely over time, so maybe you can help me out. What is the current theory about why so many of the dips appear to be preceded by a brief increase in luminosity?

I mean, the idea of a reflective body on the opposite side of the star causing the luminosity to increase may be plausible at random times, but why would it coincide so closely with dips that follow immediately thereafter? Is there any theory that explains this in plausible fashion as yet?
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/20/2017 08:45 AM
Speculation is that the current dip is like the d1540 dip in the Kepler data not d1568 as was initially thought. Meaning we should get the 8% dip next month if there is indeed a repeating pattern.

Star One

You seem to have followed the discussion about this star quite closely over time, so maybe you can help me out. What is the current theory about why so many of the dips appear to be preceded by a brief increase in luminosity?

I mean, the idea of a reflective body on the opposite side of the star causing the luminosity to increase may be plausible at random times, but why would it coincide so closely with dips that follow immediately thereafter? Is there any theory that explains this in plausible fashion as yet?

If you look at the discussions there are as many theories as stars in the sky it feels like.

On the natural side of things it seems like a ringed planet of unprecedented size is still in with strong shout.

Also orbital collision with a debris field in orbit around the star.

One thing I've seen suggested is that the material causing the d1520 dip has a different orbital period than the material causing the d1510, d1525 and d1540 dips, which appear to occupy the same orbit.

Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 06/20/2017 09:06 AM
Speculation is that the current dip is like the d1540 dip in the Kepler data not d1568 as was initially thought. Meaning we should get the 8% dip next month if there is indeed a repeating pattern.

Star One

You seem to have followed the discussion about this star quite closely over time, so maybe you can help me out. What is the current theory about why so many of the dips appear to be preceded by a brief increase in luminosity?

I mean, the idea of a reflective body on the opposite side of the star causing the luminosity to increase may be plausible at random times, but why would it coincide so closely with dips that follow immediately thereafter? Is there any theory that explains this in plausible fashion as yet?

If you look at the discussions there are as many theories as stars in the sky it feels like.

On the natural side of things it seems like a ringed planet of unprecedented size is still in with strong shout.

Also orbital collision with a debris field in orbit around the star.

One thing I've seen suggested is that the material causing the d1520 dip has a different orbital period than the material causing the d1510, d1525 and d1540 dips, which appear to occupy the same orbit.

But how would a ringed planet of huge size cause increases in luminosity immediately before so many of the dips? I mean, why would there be any correlation between the ringed planet being on the opposite side of the star and the dips from objects passing between our line of sight and the star?

That does not seem to make any sense.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/20/2017 09:27 AM
Speculation is that the current dip is like the d1540 dip in the Kepler data not d1568 as was initially thought. Meaning we should get the 8% dip next month if there is indeed a repeating pattern.

Star One

You seem to have followed the discussion about this star quite closely over time, so maybe you can help me out. What is the current theory about why so many of the dips appear to be preceded by a brief increase in luminosity?

I mean, the idea of a reflective body on the opposite side of the star causing the luminosity to increase may be plausible at random times, but why would it coincide so closely with dips that follow immediately thereafter? Is there any theory that explains this in plausible fashion as yet?

If you look at the discussions there are as many theories as stars in the sky it feels like.

On the natural side of things it seems like a ringed planet of unprecedented size is still in with strong shout.

Also orbital collision with a debris field in orbit around the star.

One thing I've seen suggested is that the material causing the d1520 dip has a different orbital period than the material causing the d1510, d1525 and d1540 dips, which appear to occupy the same orbit.

But how would a ringed planet of huge size cause increases in luminosity immediately before so many of the dips? I mean, why would there be any correlation between the ringed planet being on the opposite side of the star and the dips from objects passing between our line of sight and the star?

That does not seem to make any sense.

That's because a number of people don't buy into the increase in luminosity as it's just an artefact in the data.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 06/20/2017 10:26 AM
You seem to have followed the discussion about this star quite closely over time, so maybe you can help me out. What is the current theory about why so many of the dips appear to be preceded by a brief increase in luminosity?

They are NOT preceded by an increase in luminosity. The apparent increase is solely an artefact of the data processing pipeline (which is essentially normalising to a multi-day moving average).

So the PDCSAP flux appears as if it has an increase, but if you look at the SAP flux, there is no increase (but it is difficult as there are all sorts of systematics in it)

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 06/20/2017 10:38 AM
Speculation is that the current dip is like the d1540 dip in the Kepler data not d1568 as was initially thought. Meaning we should get the 8% dip next month if there is indeed a repeating pattern.

That speculation is rather strained.  The timescales are 3x longer in the current dip than they were in the 1540 event, and it is exceptionally hard to think of any mechanism that would cause this.

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/20/2017 10:48 AM
Speculation is that the current dip is like the d1540 dip in the Kepler data not d1568 as was initially thought. Meaning we should get the 8% dip next month if there is indeed a repeating pattern.

That speculation is rather strained.  The timescales are 3x longer in the current dip than they were in the 1540 event, and it is exceptionally hard to think of any mechanism that would cause this.

--- Tony

Can we go back to basics here so we know where we stand do you agree or disagree that there appears to be a fit between what we are seeing now in the flux data and the Kepler data?
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 06/20/2017 11:13 AM
Can we go back to basics here so we know where we stand do you agree or disagree that there appears to be a fit between what we are seeing now in the flux data and the Kepler data?

No, I don't think there is a fit.

This seems to be the source of the speculation: https://twitter.com/DarkandWondrous/status/876702057624780801 (https://twitter.com/DarkandWondrous/status/876702057624780801)

The current dip covers 3x the time of the original and the graph has been stretched to fit.  The apparent similarity in shape is almost certainly coincidental.

If there is a strong continuing correlation in the future, I might change my mind but you seriously can't assert much from this right now

--- Tony

Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/20/2017 11:15 AM
Can we go back to basics here so we know where we stand do you agree or disagree that there appears to be a fit between what we are seeing now in the flux data and the Kepler data?

No, I don't think there is a fit.

This seems to be the source of the speculation: https://twitter.com/DarkandWondrous/status/876702057624780801 (https://twitter.com/DarkandWondrous/status/876702057624780801)

The current dip covers 3x the time of the original and the graph has been stretched to fit.  The apparent similarity in shape is almost certainly coincidental.

If there is a strong continuing correlation in the future, I might change my mind but you seriously can't assert much from this right now

--- Tony

I was under the impression that initial correlation actually came from the well respected Bruce Gary? But then that might actually be others using his data, perhaps why he now seems to be restricting this data to just a few people.

But I've also seen others on Twitter who seem to know what they are doing making some comment on it.
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 06/20/2017 11:23 AM
Can we go back to basics here so we know where we stand do you agree or disagree that there appears to be a fit between what we are seeing now in the flux data and the Kepler data?

No, I don't think there is a fit.

This seems to be the source of the speculation: https://twitter.com/DarkandWondrous/status/876702057624780801 (https://twitter.com/DarkandWondrous/status/876702057624780801)

The current dip covers 3x the time of the original and the graph has been stretched to fit.  The apparent similarity in shape is almost certainly coincidental.

If there is a strong continuing correlation in the future, I might change my mind but you seriously can't assert much from this right now

--- Tony



That being said notice the similar morphology between the event at 1540 and the little-discussed one at 1206, again with apparent differences in duration and depth.  And another possibly similar event at 360.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/20/2017 11:25 AM
As an explanation couldn't this be dust from some event as wouldn't that slow down as it was smeared around the orbit and also why the dip is shallower?
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/20/2017 03:31 PM
Initial data indicates that the dip is apparently finished for now.
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 06/20/2017 05:46 PM
Speculation is that the current dip is like the d1540 dip in the Kepler data not d1568 as was initially thought. Meaning we should get the 8% dip next month if there is indeed a repeating pattern.

That speculation is rather strained.  The timescales are 3x longer in the current dip than they were in the 1540 event, and it is exceptionally hard to think of any mechanism that would cause this.

--- Tony

What if the same object adjusted its apoapsis so that it is now transiting 3X slower?

You didn't specify any probability of the explanation being correct.
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 06/20/2017 07:11 PM
Speculation is that the current dip is like the d1540 dip in the Kepler data not d1568 as was initially thought. Meaning we should get the 8% dip next month if there is indeed a repeating pattern.

That speculation is rather strained.  The timescales are 3x longer in the current dip than they were in the 1540 event, and it is exceptionally hard to think of any mechanism that would cause this.

--- Tony

What if the same object adjusted its apoapsis so that it is now transiting 3X slower?

You didn't specify any probability of the explanation being correct.

There's nowhere near enough data to assign any sort of meaningful probability to that, or many other questions about the star. Not that it's going to stop people from doing that...
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/20/2017 07:14 PM
Speculation is that the current dip is like the d1540 dip in the Kepler data not d1568 as was initially thought. Meaning we should get the 8% dip next month if there is indeed a repeating pattern.

That speculation is rather strained.  The timescales are 3x longer in the current dip than they were in the 1540 event, and it is exceptionally hard to think of any mechanism that would cause this.

--- Tony

What if the same object adjusted its apoapsis so that it is now transiting 3X slower?

You didn't specify any probability of the explanation being correct.

There's nowhere near enough data to assign any sort of meaningful probability to that, or many other questions about the star. Not that it's going to stop people from doing that...

Quick question is it right in the case of ETI, we might see dips of arbitrary depth and duration.
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 06/20/2017 07:51 PM
Quick question is it right in the case of ETI, we might see dips of arbitrary depth and duration.
Sure, but that's a more of bug (the unconstrained nature of the ETI hypothesis) than a feature.

You can certainly imagine a swarm of objects of different sizes on various, possibly non-Keplerian orbits generating all kinds of varying patterns with or without detectable periodicity. You can equally imagine natural phenomena that produce similarly random variation, e.g. the interstellar cloud scenarios.

Only a small subset of possible ETI scenarios would be convincing from light curve data on their own, e.g. the transit of a 50,000km triangle, or blinking out sequences of prime numbers or something like that.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 06/20/2017 07:57 PM
Only a small subset of possible ETI scenarios would be convincing from light curve data on their own, e.g. the transit of a 50,000km triangle, or blinking out sequences of prime numbers or something like that.

As I remember, there's a paper on arxiv on modelling the transits of various regular shapes. [ on my phone or I'd hunt it down ]

Slightly surprisingly, I don't think anyone has modelled Niven's "Ringworld" with its inner ring of star shades yet ;-)

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/21/2017 02:27 AM
This video contains the latest Bruce Gary data for the 20th June.

https://www.youtube.com/watch?v=xniWSDOFhBk
Title: Re: Boyajians Star Updates And Discussion
Post by: high road on 06/21/2017 07:39 AM
This video contains the latest Bruce Gary data for the 20th June.

https://www.youtube.com/watch?v=xniWSDOFhBk

He keeps saying "Kepler's old data". Kepler is still watching, is it not? Any idea when the new data will be compared to the terrestrial measurements?
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 06/21/2017 07:52 AM

He keeps saying "Kepler's old data". Kepler is still watching, is it not? Any idea when the new data will be compared to the terrestrial measurements?

The Kepler K2 extended mission is no longer looking at the portion of the sky where Boyajians star is located.  It is pointed more towards Leo/Virgo.  It also no longer has the precision it used to, as two reaction wheels have failed.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/21/2017 08:17 AM

He keeps saying "Kepler's old data". Kepler is still watching, is it not? Any idea when the new data will be compared to the terrestrial measurements?

The Kepler K2 extended mission is no longer looking at the portion of the sky where Boyajians star is located.  It is pointed more towards Leo/Virgo.  It also no longer has the precision it used to, as two reaction wheels have failed.

Judging from her Twitter feed I believe Tabby has requested time on both Spitzer & HST to observe it, hopefully someone can confirm this.

It's a shame that because they are probably on a different orbital plane that any planets in the system we probably cannot see. Suspect that it does have planets, as apparently the star's metallacity tells us this.
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 06/21/2017 05:29 PM
The Kepler K2 extended mission is no longer looking at the portion of the sky where Boyajians star is located.  It is pointed more towards Leo/Virgo. It also no longer has the precision it used to, as two reaction wheels have failed.
Just to clarify a little: The K2 mission is limited to observing on the ecliptic, because that's where radiation pressure is most favorable for operation with 2 reaction wheels. The individual K2 fields can be observed for ~80 days, and available fields cover the entire ecliptic plane as Kepler orbits the Sun. See https://keplerscience.arc.nasa.gov/k2-observing.html and https://keplerscience.arc.nasa.gov/k2-fields.html

Precision is reduced somewhat, but it's still very good.

Since the original Kepler field containing Boyajian's star is well off the ecliptic, it is no longer observable by Kepler at all.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/21/2017 06:45 PM
The Kepler K2 extended mission is no longer looking at the portion of the sky where Boyajians star is located.  It is pointed more towards Leo/Virgo. It also no longer has the precision it used to, as two reaction wheels have failed.
Just to clarify a little: The K2 mission is limited to observing on the ecliptic, because that's where radiation pressure is most favorable for operation with 2 reaction wheels. The individual K2 fields can be observed for ~80 days, and available fields cover the entire ecliptic plane as Kepler orbits the Sun. See https://keplerscience.arc.nasa.gov/k2-observing.html and https://keplerscience.arc.nasa.gov/k2-fields.html

Precision is reduced somewhat, but it's still very good.

Since the original Kepler field containing Boyajian's star is well off the ecliptic, it is no longer observable by Kepler at all.

Well it be in view of TESS or PLATO?
Title: Re: Boyajians Star Updates And Discussion
Post by: Orbiter on 06/21/2017 06:48 PM
Yes, TESS will be able to observe the star. It's designed for a full-sky survey.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 06/21/2017 06:50 PM
For TESS, yes. I'm pretty sure it will be observed as it aims to be an all sky survey
For Plato, it is an ecliptic mission but I think some of the fields will overlap the Kepler field, but not sure if this will include KIC 8462852

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/21/2017 07:36 PM
Yes, TESS will be able to observe the star. It's designed for a full-sky survey.

I asked because in a recent article I read about TESS it seemed to be implying it was targeting M dwarfs so thanks for the clarification.
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 06/21/2017 07:48 PM
Well it is in a way.  TESS will be somewhat less sensitive than Kepler, this means the only places it will find rocky planets is around the smallest stars in its sample where the signal-to-noise is higher.  It isn't a Kepler substitute.
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 06/21/2017 08:17 PM
For TESS, yes. I'm pretty sure it will be observed as it aims to be an all sky survey
TESS is optimized for bright stars though. IIRC it goes down to ~mag 12, which puts Boyajian's star near the limit.

Also, while TESS is nearly all-sky (IIRC there's a gap around the ecliptic for the prime mission), coverage of each individual section is fairly short except around the poles.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/21/2017 08:38 PM
The dip might be occurring again but it's too early to say for certain at the moment. And then it got cloudy.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 06/21/2017 08:44 PM
TESS is optimized for bright stars though. IIRC it goes down to ~mag 12, which puts Boyajian's star near the limit.

Yes, I was loose when I said "observed" ... and it's worse than that really. Not only near the magnitude limit, but the TESS pixels are huge so there would almost certainly be dilution effects, making small dips very hard to see. So all in all, not likely to be useful here.

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/22/2017 06:45 PM
Latest update from Tabby confirms that the dip continues.

http://www.wherestheflux.com/single-post/2017/06/22/Dip-update-13n---dip-2-still-dipping-Kickstarter-poll-is-live

With the length of this dip they must be collecting shed loads of data on it if nothing else.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/23/2017 05:13 PM
And here's a further update from Tabby with data from Tenerife & Maui as the dip continues.

http://www.wherestheflux.com/single-post/2017/06/23/Dip-update-14n---dip-2-is-getting-up-there
Title: Re: Boyajians Star Updates And Discussion
Post by: ChrisWilson68 on 06/25/2017 05:35 AM
The June 24th video update:

https://www.youtube.com/watch?v=6LCUZGmf-WQ
Title: Re: Boyajians Star Updates And Discussion
Post by: Req on 06/25/2017 05:40 AM
Judging from her Twitter feed I believe Tabby has requested time on both Spitzer & HST to observe it, hopefully someone can confirm this.

It was mentioned at some point that Spitzer cannot observe this star, I believe during the first long Q&A video with the small panel.
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 06/25/2017 06:19 AM
It was mentioned at some point that Spitzer cannot observe this star, I believe during the first long Q&A video with the small panel.
Spitzer has observed this star (along with many others in the Kepler field), see KIC 8462852 - The Infrared Flux (https://arxiv.org/abs/1511.07908) Marengo et al.
Title: Re: Boyajians Star Updates And Discussion
Post by: Req on 06/25/2017 06:32 AM
Then that dip - they went into some detail, I just don't remember the details.  Just that there was a reason given that Spitzer couldn't observe the star for the event.
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 06/25/2017 06:56 AM
Then that dip - they went into some detail, I just don't remember the details.  Just that there was a reason given that Spitzer couldn't observe the star for the event.
Yeah, quite possible it wasn't able to observe at that time, where it can safely point varies over the orbit http://irsa.ipac.caltech.edu/data/SPITZER/docs/spitzermission/missionoverview/spitzertelescopehandbook/10/
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/25/2017 08:10 AM
Then that dip - they went into some detail, I just don't remember the details.  Just that there was a reason given that Spitzer couldn't observe the star for the event.

For the sake of clarity I was more certain she had requested time on Spitzer as I remember seeing it fairly recently on her Twitter feed. Whereas with HST it was something I had only seen reported secondhand.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/25/2017 06:57 PM
Latest updates from Tabby.

Quote
Hi everyone,
 
Here is what the latest data for the LCO station in Tenerife.  The Maui station is still taking data, I will update later today when it is finished for the night. 
 
 
~Tabby and team

http://www.wherestheflux.com/single-post/2017/06/24/Dip-update-15n---latest-on-dip2

Quote
Hi everyone,
 
Here is what the latest data for the LCO TFN station (top; unfortunately TFN had poor weather the past couple nights) and OGG (bottom).
 
After 2 weeks of dip #2, Im starting to regret the choice of my blog post names... Perhaps Ill change that soon.   
 
Lastly, one of the Kickstarter backers brought up the point that we are taking images in multiple colors. I haven't been posting these (yet) to the status updates to minimize confusion.  Tomorrow I will spend some time putting together an update including colors.

http://www.wherestheflux.com/single-post/2017/06/25/Dip-update-16n---Two-week-status-update-dip2

And here's a guest post regarding naming the dip.

http://www.wherestheflux.com/single-post/2017/06/25/Guest-post-from-astronomer-Angelle-Tanner
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/27/2017 08:16 AM
Another update from Tabby including the colour chart.

http://www.wherestheflux.com/single-post/2017/06/26/Dip-update-17n---dip2-and-data-update

Title: Re: Boyajians Star Updates And Discussion
Post by: CuddlyRocket on 06/27/2017 10:18 PM
The thing I saw was about the name of the star and using the (recognised) "Boyajian's Star" rather than "Tabby's Star".  Given you'd never dream of calling Barnard's Star "Eddie's Star" (etc), this seems a valid criticism

Barnard's Star is the IAU-approved name for GJ 699. 'Boyajian's Star' is no more (or less) recognised than 'Tabby's Star'; they're both unofficial usages.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/27/2017 10:45 PM
The thing I saw was about the name of the star and using the (recognised) "Boyajian's Star" rather than "Tabby's Star".  Given you'd never dream of calling Barnard's Star "Eddie's Star" (etc), this seems a valid criticism

Barnard's Star is the IAU-approved name for GJ 699. 'Boyajian's Star' is no more (or less) recognised than 'Tabby's Star'; they're both unofficial usages.

I thought Boyajian's star was meant to be its official name.

Just to add looking at that chart she released yesterday it was odd how at one point only blue was the most dominant, most of the time the three tracked together. But that might just be noise. Well that's what it looked like to my untrained eyes.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/28/2017 06:09 AM
Seems the star is either re-starting that last dip or starting a new one.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 06/28/2017 09:27 AM
Quote
Barnard's Star is the IAU-approved name for GJ 699. 'Boyajian's Star' is no more (or less) recognised than 'Tabby's Star'; they're both unofficial usages.

I thought Boyajian's star was meant to be its official name.

It is recognised by SIMBAD ... and follows the convention for all other stars named after people i.e. <surname>'s star. E.g. Barnard, Przybylski, Luyten, etc.

But as others have said, nomenclature is pretty off topic, so I will say no more.

Quote
Just to add looking at that chart she released yesterday it was odd how at one point only blue was the most dominant, most of the time the three tracked together. But that might just be noise. Well that's what it looked like to my untrained eyes.

The dip was deeper in blue light, which I think is consistent with dust. And I think detailed analysis should give an idea of grain size, etc.

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/28/2017 09:42 AM
Quote
Barnard's Star is the IAU-approved name for GJ 699. 'Boyajian's Star' is no more (or less) recognised than 'Tabby's Star'; they're both unofficial usages.

I thought Boyajian's star was meant to be its official name.

It is recognised by SIMBAD ... and follows the convention for all other stars named after people i.e. <surname>'s star. E.g. Barnard, Przybylski, Luyten, etc.

But as others have said, nomenclature is pretty off topic, so I will say no more.

Quote
Just to add looking at that chart she released yesterday it was odd how at one point only blue was the most dominant, most of the time the three tracked together. But that might just be noise. Well that's what it looked like to my untrained eyes.

The dip was deeper in blue light, which I think is consistent with dust. And I think detailed analysis should give an idea of grain size, etc.

--- Tony

TBH I still can't see how dust alone could either explain the long term dimming or the size of some of the dips or the periodicity. If it was just dust I don't believe these other features would be present and this matter would have been resolved a while back.

We need to see a plot for one of the large dips. So I am hoping we get one of them soon.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 06/28/2017 10:00 AM
TBH I still can't see how dust could either explain the long term dimming or the size of some of the dips or the periodicity. If it was just dust I don't believe these other features would be present.

Assuming the plane of the star's ecliptic is aligned with our line of sight, then cold, clumpy zodiacal dust around 1.6AU could explain both dips and rough periodicity (I think at this distance, Tdust is around 300K, so a deep dip should show IR emissions around 10u).  The optical depth of dust clumps is large, so deep dips are certainly feasible (as seen for some YSO dippers).

And if the zodiacal dust extends further out (where it is asymmetrically distributed around the orbit), it could also explain the secular decline.

The problem with this is how to explain how the dust is both cold *and* clumpy. If dust is a result of a recent collision, you'd expect it to be warm and detectable in IR.  And for it to be clumpy, it has to be recent - unless stabilised by some (non-transiting) larger mass.

[ the theory probably requires a second large mass as well to stabilise the more distant dust responsible for a secular decline ].

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/28/2017 10:07 AM
TBH I still can't see how dust could either explain the long term dimming or the size of some of the dips or the periodicity. If it was just dust I don't believe these other features would be present.

Assuming the plane of the star's ecliptic is aligned with our line of sight, then cold, clumpy zodiacal dust around 1.6AU could explain both dips and rough periodicity (I think at this distance, Tdust is around 300K, so a deep dip should show IR emissions around 10u).  The optical depth of dust clumps is large, so deep dips are certainly feasible (as seen for some YSO dippers).

And if the zodiacal dust extends further out (where it is asymmetrically distributed around the orbit), it could also explain the secular decline.

The problem with this is how to explain how the dust is both cold *and* clumpy. If dust is a result of a recent collision, you'd expect it to be warm and detectable in IR.  And for it to be clumpy, it has to be recent - unless stabilised by some (non-transiting) larger mass.

[ the theory probably requires a second large mass as well to stabilise the more distant dust responsible for a secular decline ].

--- Tony

Interesting that you say that as I have seen people  commenting  that something(s) and bigger than comet cores must be in the dust.

Also as people have rightly pointed out this is just data for the May dip and not the June one. Therefore probably shouldn't be extrapolating results from one to the other without data for both.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/28/2017 10:20 PM
Dip update 18/n - two months of dipping

Quote

Hi everyone,
 
 
The plots I typically share with you come from a program called AstroImageJ (AIJ) that does the aperture photometry (details of which were mentioned in a previous post; the program is freely available here). These plots are always subject to change (by small amounts) because they are binned (averaged data in a time period) and normalized (what you assume the star's "normal" brightness is, and making that =1) on the fly.
     
Ive exported from AIJ all the data for May and June and made the following graph, this time using more exact binning which includes better treatment of measurement errors, and using the normalization regions of day 0-10 and 20-35 (on the graph below you can see this as data points in these regions being evenly scattered above and below the horizontal dotted line at unity).

Your guess is as good as mine whether the dip is really over now or not, but last night shows it is back up.

http://www.wherestheflux.com/single-post/2017/06/28/Dip-update-18n---two-months-of-dipping
Title: Re: Boyajians Star Updates And Discussion
Post by: CuddlyRocket on 06/29/2017 03:26 AM
Quote
Barnard's Star is the IAU-approved name for GJ 699. 'Boyajian's Star' is no more (or less) recognised than 'Tabby's Star'; they're both unofficial usages.

I thought Boyajian's star was meant to be its official name.

It is recognised by SIMBAD ...

SIMBAD is not the IAU. Apart from the fact it occasionally makes mistakes, it records traditional, historical and common usage of names that may or may not be approved by the IAU under its (relatively new) formal procedure for naming stars. Barnards' Star is an IAU approved name and the star is listed as such on the List of IAU-approved Star Names (https://www.iau.org/public/themes/naming_stars/); Boyajian's Star (or Tabby's Star) is not.

Quote
... and follows the convention for all other stars named after people i.e. <surname>'s star. E.g. Barnard, Przybylski, Luyten, etc.

A common practice, rather than a convention; and one not necessarily followed by the IAU. For instance, the stars Cervantes, Copernicus, Rotanev and Sualocin are named after people with IAU-approved names.

Quote
But as others have said, nomenclature is pretty off topic, so I will say no more.

Well, the thread title simply says 'discussion', not 'discussion limited to physical properties' and the OP is silent on the matter. But, I was mainly concerned to correct a misapprehension, not to monopolise or derail the thread, so happy to let it rest there!
Title: Re: Boyajians Star Updates And Discussion
Post by: gospacex on 06/29/2017 10:03 AM
Did ALMA try to image the star? Its best resolution is 20 mas (although I don't know whether they already demonstrated it, ALMA is still young). This might be enough to actually see dust disks, if there are any.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/29/2017 11:27 AM
Did ALMA try to image the star? Its best resolution is 20 mas (although I don't know whether they already demonstrated it, ALMA is still young). This might be enough to actually see dust disks, if there are any.

I don't know if those who supported the Kickstarter get this kind of info or whether for now the team are keeping this kind of info under their collective hats until any papers appear.

Anyway it's not so much the dust itself as accounting for its behaviour as it seems possible there is something more solid in it that's causing this from my understanding of the more learned on the topic.
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 06/29/2017 12:57 PM
Did ALMA try to image the star? Its best resolution is 20 mas (although I don't know whether they already demonstrated it, ALMA is still young). This might be enough to actually see dust disks, if there are any.

Too low in the sky for ALMA unfortunately.
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 06/29/2017 12:58 PM
Did ALMA try to image the star? Its best resolution is 20 mas (although I don't know whether they already demonstrated it, ALMA is still young). This might be enough to actually see dust disks, if there are any.

The problem is that the star never gets high in the sky at ALMA site. Its maximum elevation there is about 23 degrees, while the lowest possible elevation for ALMA observations is (I believe) 20 degrees. So it would be (just barely) possible to observe it for a short while, but data quality will not be good (due to bad uv coverage, large airmass, shadowing, etc.).
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/30/2017 01:06 PM
More on the AAVSO trends for Boyajian's Star

https://disownedsky.blogspot.co.uk/2017/06/more-on-aavso-trends-for-boyajians-star.html

I do have a suspicion that sometimes the long term dimming is downplayed because it doesn't fit in with some theories.
Title: Re: Boyajians Star Updates And Discussion
Post by: gospacex on 06/30/2017 01:09 PM
Did ALMA try to image the star? Its best resolution is 20 mas (although I don't know whether they already demonstrated it, ALMA is still young). This might be enough to actually see dust disks, if there are any.

Too low in the sky for ALMA unfortunately.

Then VLBA should be able to see it. It has even better resolution of 0.17 mas, but can only go down to 7mm wavelength... I'm not even close to knowing whether that's useful.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 06/30/2017 07:27 PM
A number of people have proposed that the current dip is not unlike the D1200 event in the Kepler data.
Title: Re: Boyajians Star Updates And Discussion
Post by: jgoldader on 06/30/2017 11:34 PM
On VLBA--7mm is "colder" than the cosmic microwave background (peak at 1mm for ~3K blackbody), so you probably wouldn't see even the tail of blackbody emission from dust around a star, which should be a lot warmer.  At those wavelengths, AFAI remember, you'd get only non-thermal emission, like synchrotron or free-free emission, neither of which I'd expect in abundance from an F-type star, and especially not from anything far from the photosphere of an F-type star.  Any radio emission would be, I suppose, from the photosphere or just above it, as we do see in our own Sun.
Title: Re: Boyajians Star Updates And Discussion
Post by: Mongo62 on 07/01/2017 12:28 AM
For those who aren't aware, Fredric Parker puts out nearly-daily videos with updates on Boyajian's Star. Here is today's video:

https://www.youtube.com/watch?v=uvwrAABZ74w
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/01/2017 10:01 AM
Latest Bruce Gary data up to today suggests we might be seeing another dip.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/01/2017 05:00 PM
If this is dust to some degree then something must be replenishing it otherwise the star's solar wind would clear it from the system.
Title: Re: Boyajians Star Updates And Discussion
Post by: RotoSequence on 07/01/2017 05:05 PM
If this is dust to some degree then something must be replenishing it otherwise the star's solar wind would clear it from the system.

It's possible that we won the cosmic timeline lottery and are watching a shortlived phenomenon while it's active.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/01/2017 05:08 PM
If this is dust to some degree then something must be replenishing it otherwise the star's solar wind would clear it from the system.

It's possible that we won the cosmic timeline lottery and are watching a shortlived phenomenon while it's active.
But odds would say that's unlikely though.
Title: Re: Boyajians Star Updates And Discussion
Post by: RotoSequence on 07/01/2017 05:21 PM
If this is dust to some degree then something must be replenishing it otherwise the star's solar wind would clear it from the system.

It's possible that we won the cosmic timeline lottery and are watching a shortlived phenomenon while it's active.
But odds would say that's unlikely though.

There's not a whole lot about this star's behavior that isn't unlikely.  ;)
Title: Re: Boyajians Star Updates And Discussion
Post by: jgoldader on 07/01/2017 09:31 PM
(Highly unlikely behavior) * (lots of stars) = good chance of seeing it.

But *what* we're seeing... aye, there's the question!
Title: Re: Boyajians Star Updates And Discussion
Post by: Mongo62 on 07/01/2017 10:46 PM
It's possible that we won the cosmic timeline lottery and are watching a shortlived phenomenon while it's active.
But odds would say that's unlikely though.

If this were the only star we were watching, yes. But given the number of stars being monitored, it's entirely possible (indeed very likely) that we are seeing some phenomenon that's very short-lived in astronomical terms.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/01/2017 10:54 PM
It's possible that we won the cosmic timeline lottery and are watching a shortlived phenomenon while it's active.
But odds would say that's unlikely though.

If there were the only star we were watching, yes. But given the number of stars being monitored, it's entirely possible (indeed very likely) that we are seeing some phenomenon that's very short-lived in astronomical terms.

I find that stretches credibility too far.
Title: Re: Boyajians Star Updates And Discussion
Post by: meekGee on 07/02/2017 12:07 AM
It's possible that we won the cosmic timeline lottery and are watching a shortlived phenomenon while it's active.
But odds would say that's unlikely though.

If this were the only star we were watching, yes. But given the number of stars being monitored, it's entirely possible (indeed very likely) that we are seeing some phenomenon that's very short-lived in astronomical terms.

Exactly.  And we were drawn to this star BECAUSE of this behavior, thus nulling the odds.

It's like you look at a population of 1,000,000 people, and specifically hunt for crazy behavior.  Then you find one, and my god!  the man is crazy!  What are the odds?
Title: Re: Boyajians Star Updates And Discussion
Post by: KelvinZero on 07/02/2017 05:01 AM
Exactly.  And we were drawn to this star BECAUSE of this behavior, thus nulling the odds.

It's like you look at a population of 1,000,000 people, and specifically hunt for crazy behavior.  Then you find one, and my god!  the man is crazy!  What are the odds?
Probably just clarifying what you are saying, when you say crazy, you mean a diverse set of things we would lump under 'crazy', not a specific well defined crazy.

If you look at a hundred stars and see a 1/trillion event, that does not mean the odds were 100/trillion, the odds were 100*(the number of possible events that we would consider really 1:trillion weird)/trillion
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/02/2017 07:55 AM
It's possible that we won the cosmic timeline lottery and are watching a shortlived phenomenon while it's active.
But odds would say that's unlikely though.

If this were the only star we were watching, yes. But given the number of stars being monitored, it's entirely possible (indeed very likely) that we are seeing some phenomenon that's very short-lived in astronomical terms.

Exactly.  And we were drawn to this star BECAUSE of this behavior, thus nulling the odds.

It's like you look at a population of 1,000,000 people, and specifically hunt for crazy behavior.  Then you find one, and my god!  the man is crazy!  What are the odds?
But it wasn't apparently the only star that Kepler looked at that seemed to be behaving oddly. It's just it has had the follow up the others haven't.
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 07/02/2017 08:12 AM
But it wasn't apparently the only star that Kepler looked at that seemed to be behaving oddly. It's just it has had the follow up the others haven't.

I'm not aware of anything other behaving nearly this oddly. Some run-of-the-mill oddness can of course be found in more or less every star, if looked close enough.

Anyway, if the secular dimming is real, we are looking at a relatively short-lived event in astronomical terms, no matter what is causing it. A star can't keep dimming ~20 percent per century for very long before it's no longer observable.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/02/2017 08:27 AM
https://www.youtube.com/watch?v=bFxKDY9-4JY

This star just gets stranger now it appears there might be pulsations in the signal. So is the star variable.

If this is real it must be the star as dust is not known to pulse.
Title: Re: Boyajians Star Updates And Discussion
Post by: LouScheffer on 07/02/2017 12:11 PM
It's possible that we won the cosmic timeline lottery and are watching a shortlived phenomenon while it's active.
But odds would say that's unlikely though.
If this were the only star we were watching, yes. But given the number of stars being monitored, it's entirely possible (indeed very likely) that we are seeing some phenomenon that's very short-lived in astronomical terms.
Einstein predicted gravitational lensing, but concluded that since a most unlikely alignment is needed, it only lasts a few days, and it never repeats, "there is no great chance of observing this phenomenon".   He was correct that the needed alignment is very rare, but microlensing surveys get around this by monitoring millions of stars for many years.  So per star, it's very unlikely, but if you watch enough stars, you'll see it.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/02/2017 12:15 PM
It's possible that we won the cosmic timeline lottery and are watching a shortlived phenomenon while it's active.
But odds would say that's unlikely though.
If this were the only star we were watching, yes. But given the number of stars being monitored, it's entirely possible (indeed very likely) that we are seeing some phenomenon that's very short-lived in astronomical terms.
Einstein predicted gravitational lensing, but concluded that since a most unlikely alignment is needed, it only lasts a few days, and it never repeats, "there is no great chance of observing this phenomenon".   He was correct that the needed alignment is very rare, but microlensing surveys get around this by monitoring millions of stars for many years.  So per star, it's very unlikely, but if you watch enough stars, you'll see it.

The problem with this argument is you could just as easily apply to ETI, yet people are more willing to accept a natural explanation when in fact they are both equally unlikely or likely depending on your viewpoint.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/02/2017 06:35 PM
https://www.youtube.com/watch?v=hjbs4ShcI4k
Title: Re: Boyajians Star Updates And Discussion
Post by: meekGee on 07/02/2017 06:58 PM
It's possible that we won the cosmic timeline lottery and are watching a shortlived phenomenon while it's active.
But odds would say that's unlikely though.
If this were the only star we were watching, yes. But given the number of stars being monitored, it's entirely possible (indeed very likely) that we are seeing some phenomenon that's very short-lived in astronomical terms.
Einstein predicted gravitational lensing, but concluded that since a most unlikely alignment is needed, it only lasts a few days, and it never repeats, "there is no great chance of observing this phenomenon".   He was correct that the needed alignment is very rare, but microlensing surveys get around this by monitoring millions of stars for many years.  So per star, it's very unlikely, but if you watch enough stars, you'll see it.

The problem with this argument is you could just as easily apply to ETI, yet people are more willing to accept a natural explanation when in fact they are both equally unlikely or likely depending on your viewpoint.

How so?

ETI is about cause.  The argument is about observations, and about phenomena being transient, whatever their cause may be.

The argument says that the odds of observing a transient phenomena, when observing a huge star field and specifically hunting for "abnormal" behaviors is not slim.

In astronomy, when you start by looking at a specific star, it is customary to discount transient phenomena, since "what are the odds".  And that's a valid methodology.

It shouldn't be applied to Kepler-like observations, however. It is quite likely that Kepler will catch some transients happening, and BS may be just one such.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/02/2017 07:37 PM
New interview with Jason Wright.

http://blogs.discovermagazine.com/outthere/2017/06/30/wright/
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/03/2017 07:00 AM
Latest update.

Quote
Here is the combined light curve for dates June 1 - July 2 using daily average data from both the OGG and TFN sites. Often times there is agreement between sites with the "adjacent" observations, taken ~12 hours apart.  On the other hand, we can possibly see variability on timescales less than a day, too (look at data taken between days ~44-48).  Neat!

http://www.wherestheflux.com/single-post/2017/07/02/Dip-update-22n
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 07/03/2017 07:25 AM
Question:

Have these tiny light fluctuations of the last month or so (less than 0.5% of the flux) been going on for all of the past year while news from the star has been virtually zero? Or was the star pretty dead in terms of light fluctuations until the May dip suddenly kick started a new period of small scale variability?

What I'm trying to get at is people are now suddenly getting daily updates from Gary Bruce and others about every minute fluctuation, and coming up with all kinds of questions and theories about it. But before that, all we were really waiting for were the 8%, 15% and 22% dips. Were the small fluctuations simply not getting much attention until recently, or did they only start increasing in frequency after the May dip, which started the current cycle of interest in the star?
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 07/03/2017 07:38 AM
Have these tiny light fluctuations of the last month or so (less than 0.5% of the flux) been going on for all of the past year while news from the star has been virtually zero? Or was the star pretty dead in terms of light fluctuations until the May dip suddenly kick started a new period of small scale variability?
It was observed to be stable within the uncertainties for a significant time before, by Boyajian's group and others. The May dip was the first conclusive dip since Kepler that they recognized. Of course there could have been dips that were missed in the parts of the year the star isn't observable, or due to weather etc.

edit:
Here's an update reporting no (real) dips http://www.wherestheflux.com/single-post/2017/01/03/November-science-update
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/03/2017 07:54 AM
Question:

Have these tiny light fluctuations of the last month or so (less than 0.5% of the flux) been going on for all of the past year while news from the star has been virtually zero? Or was the star pretty dead in terms of light fluctuations until the May dip suddenly kick started a new period of small scale variability?

What I'm trying to get at is people are now suddenly getting daily updates from Gary Bruce and others about every minute fluctuation, and coming up with all kinds of questions and theories about it. But before that, all we were really waiting for were the 8%, 15% and 22% dips. Were the small fluctuations simply not getting much attention until recently, or did they only start increasing in frequency after the May dip, which started the current cycle of interest in the star?

From my rough understanding it seems to have all kicked off with the May dip, before then the star appears to have been behaving fairly normally for this class of star.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/03/2017 07:19 PM
Latest update is that the star's brightness is back to normal for now.
Title: Re: Boyajians Star Updates And Discussion
Post by: ChrisWilson68 on 07/03/2017 10:32 PM
This star just gets stranger now it appears there might be pulsations in the signal. So is the star variable.

If this is real it must be the star as dust is not known to pulse.

Not true.  Even if it's real it doesn't mean dust is ruled out.  The video you got this information from even mentions this.  It could be dust with structure, for example dust rotating around an object.  Or it could be that the pulsing is in the star but unrelated to the other dipping that has been seen.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/03/2017 10:34 PM
This star just gets stranger now it appears there might be pulsations in the signal. So is the star variable.

If this is real it must be the star as dust is not known to pulse.

Not true.  Even if it's real it doesn't mean dust is ruled out.  The video you got this information from even mentions this.  It could be dust with structure, for example dust rotating around an object.  Or it could be that the pulsing is in the star but unrelated to the other dipping that has been seen.

Since when can dust pulse, a star I can accept but dust?
Title: Re: Boyajians Star Updates And Discussion
Post by: ChrisWilson68 on 07/03/2017 11:26 PM
This star just gets stranger now it appears there might be pulsations in the signal. So is the star variable.

If this is real it must be the star as dust is not known to pulse.

Not true.  Even if it's real it doesn't mean dust is ruled out.  The video you got this information from even mentions this.  It could be dust with structure, for example dust rotating around an object.  Or it could be that the pulsing is in the star but unrelated to the other dipping that has been seen.

Since when can dust pulse, a star I can accept but dust?

Part of the problem is the terminology you're using.  You're defining a short-term cyclical dimming pattern (on the order of an hour cycle time) as "pulsing".    Then you're implying that if the dust is the root cause of this pattern, the dust must be "pulsing".  But under no model is the dust the source of light, rather it's supposed to block some of the light from the star.  So, if the dust is the cause of the cyclical dimming, it wouldn't be that the dust is pulsing so much as it would be that the dust has some sort of periodic behavior on the order of an hour.

We don't really know what would cause that, but then again we don't have any explanation that is consistent with the data.  So claiming that it can't be in the dust because we don't have a model using dust that explains it isn't valid because we have no model not using dust that explains it either.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/04/2017 06:49 AM
This star just gets stranger now it appears there might be pulsations in the signal. So is the star variable.

If this is real it must be the star as dust is not known to pulse.

Not true.  Even if it's real it doesn't mean dust is ruled out.  The video you got this information from even mentions this.  It could be dust with structure, for example dust rotating around an object.  Or it could be that the pulsing is in the star but unrelated to the other dipping that has been seen.

Since when can dust pulse, a star I can accept but dust?

Part of the problem is the terminology you're using.  You're defining a short-term cyclical dimming pattern (on the order of an hour cycle time) as "pulsing".    Then you're implying that if the dust is the root cause of this pattern, the dust must be "pulsing".  But under no model is the dust the source of light, rather it's supposed to block some of the light from the star.  So, if the dust is the cause of the cyclical dimming, it wouldn't be that the dust is pulsing so much as it would be that the dust has some sort of periodic behavior on the order of an hour.

We don't really know what would cause that, but then again we don't have any explanation that is consistent with the data.  So claiming that it can't be in the dust because we don't have a model using dust that explains it isn't valid because we have no model not using dust that explains it either.
For the sake of clarity I didn't mean to apply that dust was the root cause rather that I thought of the two that the star was the more likely cause for this particular observation.

Anyway here is the latest update.

Quote
All,

Small update here showing the latest OGG + TFN light curve.  It looks like for the past 24 hours the flux has returned to normal.

http://www.wherestheflux.com/single-post/2017/07/03/Dip-update-23n---combined-curve-from-TFN-and-OGG---24h-of-normal-flux

Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/04/2017 08:15 PM
Today's update from Professor Boyajian to quote:

Quote
brightness is 0.5% depressed, which is "borderline significant". The second dip is named "Celeste." The next one will probably be "Skara Brae."

https://www.youtube.com/watch?v=Lu6FBcYCAs4
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/05/2017 06:49 PM
Latest update & it does indeed look like we are heading into another dip with the last 48 hours showing the star's flux has been 0.5% below normal.

http://www.wherestheflux.com/single-post/2017/07/05/Dip-update-24n---Celeste-chosen-for-the-name-of-the-June-2017-dip
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/06/2017 12:35 AM
The 24.2 day cycle can now hopefully be tested. See the new video below for a fuller explanation and prediction regarding the 6th July.

https://www.youtube.com/watch?v=G0oLfPM4rnw
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/06/2017 03:52 PM
Quote
Hi everyone,
 
This is the current light curve graph in r'-band for June - July. Nothing notable just yet.     
 
~Tabby and team

http://www.wherestheflux.com/single-post/2017/07/06/Dip-update-25n---daily-dose-of-flux
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/07/2017 06:37 PM
Via Reddit.

Quote
Latest e-mail from Tabby shows LCGO data holding steady. About 0.5% down from the baseline 60 days ago. This is not altogether inconsistent with superimposed long period dimming.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/07/2017 08:22 PM
Their request for time on the HST has been rejected.

Quote
Hi everyone,
 
Below are the latest from TFN and OGG.
 
We also heard back from the folks that run the Hubble Space Telescope about our proposals (we submitted two proposals, almost identical to each other.  One was a regular cycle proposal for Target of Opportunity (ToO) observations, the other was a DD (Directors Discretionary) proposal in case the circumstances (a dip) happened before the regular cycle observations started.  Unfortunately they had low rankings from review panel and were neither were allocated any time. The main objection to the proposal was that we should have "been more explicit in requesting the timescale of the ToO observations." While this is a fair complaint, it is difficult to pin this time down precisely with such a transient object! Anyway, we plan to work on revising the proposal folding in this feedback from the review panel. 
 
Over the weekend, I will post brief data updates here on the blog. 
 
~Tabby and team

http://www.wherestheflux.com/single-post/2017/07/07/Dip-update-26n---data-and-proposal-updates
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/07/2017 09:09 PM
https://www.youtube.com/watch?v=aUI0oVN2Oa4
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/07/2017 11:51 PM
Seems like this star is now dimming at an accelerating rate. That doesn't seem like something that would fit with dust but rather the star itself.
Title: Re: Boyajians Star Updates And Discussion
Post by: moreno7798 on 07/08/2017 04:47 AM
Could I be so bold as to suggest that perhaps we're looking at the death of a star. As we have been shown time and again, the universe never fails to surprise us. Perhaps "SOME" stars do not die slowly (billions of years) through the usual process of exhaustion of nuclear fusion. Maybe . . .just maybe some stars have "sudden Deaths" (perhaps in the thousands of years as opposed to billions).

It's possible we're witnessing the star equivalent of a human heart attack. Stars may be much more unpredictable than we ever thought.

Just a thought.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/08/2017 09:03 AM
Could I be so bold as to suggest that perhaps we're looking at the death of a star.As we have been shown time and again, the universe never fails to surprise us. Perhaps "SOME" stars do not die slowly (billions of years) through the usual process of exhaustion of nuclear fusion. Maybe . . .just maybe some stars have "sudden Deaths" (perhaps in the thousands of years as opposed to billions).

It's possible we're witnessing the star equivalent of a human heart attack. Stars may be much more unpredictable than we ever thought.

Just a thought.

https://www.sciencealert.com/how-mysterious-disappearing-stars-could-point-us-towards-alien-life
Title: Re: Boyajians Star Updates And Discussion
Post by: ChrisWilson68 on 07/08/2017 06:18 PM
Seems like this star is now dimming at an accelerating rate. That doesn't seem like something that would fit with dust but rather the star itself.

I don't see any reason to think that.

We don't have a theory, either of the star itself or of dust, that fits all the data yet.  There's no particular reason to think accelerated long-term dimming would be more consistent with one theory or the other.  There are certainly conditions under which there could be spreading dust clouds, or cascading collisions producing more and more dust that would accelerate long-term dimming.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/08/2017 06:20 PM
Seems like this star is now dimming at an accelerating rate. That doesn't seem like something that would fit with dust but rather the star itself.

I don't see any reason to think that.

We don't have a theory, either of the star itself or of dust, that fits all the data yet.  There's no particular reason to think accelerated long-term dimming would be more consistent with one theory or the other.  There are certainly conditions under which there could be spreading dust clouds, or cascading collisions producing more and more dust that would accelerate long-term dimming.

If the star keeps going the way it is, it will be extinguished from our view within a century which seems a heck of a lot to ask from dust.
Title: Re: Boyajians Star Updates And Discussion
Post by: ChrisWilson68 on 07/08/2017 06:28 PM
Seems like this star is now dimming at an accelerating rate. That doesn't seem like something that would fit with dust but rather the star itself.

I don't see any reason to think that.

We don't have a theory, either of the star itself or of dust, that fits all the data yet.  There's no particular reason to think accelerated long-term dimming would be more consistent with one theory or the other.  There are certainly conditions under which there could be spreading dust clouds, or cascading collisions producing more and more dust that would accelerate long-term dimming.

If the star keeps going the way it is, it will be extinguished from our view within a century which seems a heck of a lot to ask from dust.

If that happens, it would be a lot to ask from dust, but there's really very little reason to project the current trends forward that far.  We don't know why it's been dimming, so we don't know how far the dimming will continue.
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 07/08/2017 07:14 PM
Maybe a trivial question, but is there anyone who would actually be satisfied if it turns out to be mere dust?
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 07/08/2017 07:40 PM
If the star keeps going the way it is, it will be extinguished from our view within a century which seems a heck of a lot to ask from dust.
As ChrisWilson68 says, there's no justification to assume it will follow the current trajectory indefinitely, but in any case, it's a lot easier for dust than internal stellar processes! There are dust clouds that are essentially 100% opaque at optical wavelengths. Blotting out just one star would be weird and improbable but it's physically plausible at a BOTE level. The same cannot be said of a star intrinsically fading to nothing on century timescales.

FWIW, here's a somewhat recent article on a paper suggesting internal stellar processes: http://aasnova.org/2017/07/07/another-possibility-for-boyajians-star/ (arxiv link for the paper https://arxiv.org/abs/1704.00070)

The arguments against this kind of explanation have generally been
1) Stars like this haven't been observed to do this, and models don't predict anything like it, which makes a "normal" stellar process unlikely
2) Anything associated with star spots or other features reaching the outer layers of the star would modulated by the stars rotation, which is not seen.

#1 can avoided if this only happens in a very narrow mass range or for a relatively short fraction of the stars life. As Foukal notes, Kepler observed relatively few stars of this type, so it need not be as rare as the overall Kepler statistics suggest. #2 can perhaps be avoided if the process is deep within the star.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/08/2017 08:08 PM
If the star keeps going the way it is, it will be extinguished from our view within a century which seems a heck of a lot to ask from dust.
As ChrisWilson68 says, there's no justification to assume it will follow the current trajectory indefinitely, but in any case, it's a lot easier for dust than internal stellar processes! There are dust clouds that are essentially 100% opaque at optical wavelengths. Blotting out just one star would be weird and improbable but it's physically plausible at a BOTE level. The same cannot be said of a star intrinsically fading to nothing on century timescales.

FWIW, here's a somewhat recent article on a paper suggesting internal stellar processes: http://aasnova.org/2017/07/07/another-possibility-for-boyajians-star/ (arxiv link for the paper https://arxiv.org/abs/1704.00070)

The arguments against this kind of explanation have generally been
1) Stars like this haven't been observed to do this, and models don't predict anything like it, which makes a "normal" stellar process unlikely
2) Anything associated with star spots or other features reaching the outer layers of the star would modulated by the stars rotation, which is not seen.

#1 can avoided if this only happens in a very narrow mass range or for a relatively short fraction of the stars life. As Foukal notes, Kepler observed relatively few stars of this type, so it need not be as rare as the overall Kepler statistics suggest. #2 can perhaps be avoided if the process is deep within the star.

I disagree that there's no justification for believing  it will continue the current trajectory when we already have a degree of evidence to indicate that it has been dimming over a long time.
Title: Re: Boyajians Star Updates And Discussion
Post by: ChrisWilson68 on 07/08/2017 08:48 PM
If the star keeps going the way it is, it will be extinguished from our view within a century which seems a heck of a lot to ask from dust.
As ChrisWilson68 says, there's no justification to assume it will follow the current trajectory indefinitely, but in any case, it's a lot easier for dust than internal stellar processes! There are dust clouds that are essentially 100% opaque at optical wavelengths. Blotting out just one star would be weird and improbable but it's physically plausible at a BOTE level. The same cannot be said of a star intrinsically fading to nothing on century timescales.

FWIW, here's a somewhat recent article on a paper suggesting internal stellar processes: http://aasnova.org/2017/07/07/another-possibility-for-boyajians-star/ (arxiv link for the paper https://arxiv.org/abs/1704.00070)

The arguments against this kind of explanation have generally been
1) Stars like this haven't been observed to do this, and models don't predict anything like it, which makes a "normal" stellar process unlikely
2) Anything associated with star spots or other features reaching the outer layers of the star would modulated by the stars rotation, which is not seen.

#1 can avoided if this only happens in a very narrow mass range or for a relatively short fraction of the stars life. As Foukal notes, Kepler observed relatively few stars of this type, so it need not be as rare as the overall Kepler statistics suggest. #2 can perhaps be avoided if the process is deep within the star.

I disagree that there's no justification for believing  it will continue the current trajectory when we already have a degree of evidence to indicate that it has been dimming over a long time.

Suppose we had been watching in real time during the recent short-term 8% or 22% dips and someone had said, "Hey, there's an accelerating dimming.  If it follows current trends, it will go to 0 in 7 more days.  I believe it will do that."  That person would have been wrong.  Even before that person was proven wrong, though, by the flux rebounding, other people could reasonably have said it wasn't justified to assume the dimming trend would continue all the way to zero.

In my opinion, your believe that it's likely the long-term dimming trend will continue to zero is just as much unjustified.  It's the same situation, just on a longer time scale.  Sure, we don't know, it's possible it will follow the trend to zero.  But there's no reason to believe the trend will continue to zero.  Since we don't know what's causing it, we shouldn't make assumptions about how far it will continue.

There are lots of known processes that can dim stars to some degree but not to zero.  We don't know what process is responsible for the long term dimming in Tabby's star, but it seems probable to me it shares with those other processes the trait that it will stop long before reaching zero flux.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/08/2017 08:59 PM
If the star keeps going the way it is, it will be extinguished from our view within a century which seems a heck of a lot to ask from dust.
As ChrisWilson68 says, there's no justification to assume it will follow the current trajectory indefinitely, but in any case, it's a lot easier for dust than internal stellar processes! There are dust clouds that are essentially 100% opaque at optical wavelengths. Blotting out just one star would be weird and improbable but it's physically plausible at a BOTE level. The same cannot be said of a star intrinsically fading to nothing on century timescales.

FWIW, here's a somewhat recent article on a paper suggesting internal stellar processes: http://aasnova.org/2017/07/07/another-possibility-for-boyajians-star/ (arxiv link for the paper https://arxiv.org/abs/1704.00070)

The arguments against this kind of explanation have generally been
1) Stars like this haven't been observed to do this, and models don't predict anything like it, which makes a "normal" stellar process unlikely
2) Anything associated with star spots or other features reaching the outer layers of the star would modulated by the stars rotation, which is not seen.

#1 can avoided if this only happens in a very narrow mass range or for a relatively short fraction of the stars life. As Foukal notes, Kepler observed relatively few stars of this type, so it need not be as rare as the overall Kepler statistics suggest. #2 can perhaps be avoided if the process is deep within the star.

I disagree that there's no justification for believing  it will continue the current trajectory when we already have a degree of evidence to indicate that it has been dimming over a long time.

Suppose we had been watching in real time during the recent short-term 8% or 22% dips and someone had said, "Hey, there's an accelerating dimming.  If it follows current trends, it will go to 0 in 7 more days.  I believe it will do that."  That person would have been wrong.  Even before that person was proven wrong, though, by the flux rebounding, other people could reasonably have said it wasn't justified to assume the dimming trend would continue all the way to zero.

In my opinion, your believe that it's likely the long-term dimming trend will continue to zero is just as much unjustified.  It's the same situation, just on a longer time scale.  Sure, we don't know, it's possible it will follow the trend to zero.  But there's no reason to believe the trend will continue to zero.  Since we don't know what's causing it, we shouldn't make assumptions about how far it will continue.

There are lots of known processes that can dim stars to some degree but not to zero.  We don't know what process is responsible for the long term dimming in Tabby's star, but it seems probable to me it shares with those other processes the trait that it will stop long before reaching zero flux.

Other than the fact your misrepresenting the argument regarding the possible evidence I was referring to which is from the photographic plates examined covering many years in time for the long term dimming trend.
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 07/08/2017 09:08 PM
Another Possibility for Boyajian’s Star
That's literally what I linked in the post you quoted just above ;)

Quote
I disagree that there's no justification for believing  it will continue the current trajectory when we already have a degree of evidence to indicate that it has been dimming over a long time.
Surely that depends on the nature of the (unknown) underlying process? If it's intrinsic to the star, it really has to bottom out or reverse at some point far from 0.

Sure, in the short term, it's unlikely we noticed it exactly at the bottom of a multi-century event, but in the long term, a main sequence star has a certain energy budget and that energy is going to get out. Only something between us and the star could reduce the flux we receive to an arbitrarily low value.
Title: Re: Boyajians Star Updates And Discussion
Post by: ChrisWilson68 on 07/08/2017 09:14 PM
Other than the fact your misrepresenting the argument regarding the possible evidence I was referring to which is from the photographic plates examined covering many years in time for the long term dimming trend.

You must be misunderstanding my argument because for my argument it's irrelevant where the evidence is coming from or what the timescale is.  My argument is that even if we accept that there is a dimming trend, on any timescale, it's not justified to assume that dimming trend will continue to zero.  It doesn't matter if the timescale is 2 days or 600 days or 150 years.  It also doesn't matter if the dimming is by 0.5% or 50%.  If you think any of those things matter to my argument, you're not understanding my argument.
Title: Re: Boyajians Star Updates And Discussion
Post by: gospacex on 07/08/2017 09:20 PM
I disagree that there's no justification for believing  it will continue the current trajectory when we already have a degree of evidence to indicate that it has been dimming over a long time.

It may continue this trajectory, but eventually settle to a _nonzero_ luminosity.
For example, this sometimes happen to stars experiencing weak helium flash. They brighten, then dim. Each process taking thousands of years.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/08/2017 10:09 PM
Other than the fact your misrepresenting the argument regarding the possible evidence I was referring to which is from the photographic plates examined covering many years in time for the long term dimming trend.

You must be misunderstanding my argument because for my argument it's irrelevant where the evidence is coming from or what the timescale is.  My argument is that even if we accept that there is a dimming trend, on any timescale, it's not justified to assume that dimming trend will continue to zero.  It doesn't matter if the timescale is 2 days or 600 days or 150 years.  It also doesn't matter if the dimming is by 0.5% or 50%.  If you think any of those things matter to my argument, you're not understanding my argument.

At least on my side of the discussion I have some basis in data, something that you don't have. You seem to have come up with an argument that just ignores any evidence contrary to your belief.
Title: Re: Boyajians Star Updates And Discussion
Post by: ChrisWilson68 on 07/08/2017 11:06 PM
Other than the fact your misrepresenting the argument regarding the possible evidence I was referring to which is from the photographic plates examined covering many years in time for the long term dimming trend.

You must be misunderstanding my argument because for my argument it's irrelevant where the evidence is coming from or what the timescale is.  My argument is that even if we accept that there is a dimming trend, on any timescale, it's not justified to assume that dimming trend will continue to zero.  It doesn't matter if the timescale is 2 days or 600 days or 150 years.  It also doesn't matter if the dimming is by 0.5% or 50%.  If you think any of those things matter to my argument, you're not understanding my argument.

At least on my side of the discussion I have some basis in data, something that you don't have. You seem to have come up with an argument that just ignores any evidence contrary to your belief.

Not true in the slightest.  I'm just questioning your evidence.  It's valid to question someone else's conclusions without presenting evidence to the contrary if the argument is that the evidence that other person presented is not valid.

It's analagous to you claiming someone is a murderer because an astrologer told you so.  Then when I question whether an astrologer is really valid evidence you claim that my argument just ignores any evidence contrary to my belief.  No.  I'm just saying you've reached an invalid conclusion because an astrologer is not valid evidence.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/08/2017 11:37 PM
Other than the fact your misrepresenting the argument regarding the possible evidence I was referring to which is from the photographic plates examined covering many years in time for the long term dimming trend.

You must be misunderstanding my argument because for my argument it's irrelevant where the evidence is coming from or what the timescale is.  My argument is that even if we accept that there is a dimming trend, on any timescale, it's not justified to assume that dimming trend will continue to zero.  It doesn't matter if the timescale is 2 days or 600 days or 150 years.  It also doesn't matter if the dimming is by 0.5% or 50%.  If you think any of those things matter to my argument, you're not understanding my argument.

At least on my side of the discussion I have some basis in data, something that you don't have. You seem to have come up with an argument that just ignores any evidence contrary to your belief.

Not true in the slightest.  I'm just questioning your evidence.  It's valid to question someone else's conclusions without presenting evidence to the contrary if the argument is that the evidence that other person presented is not valid.

It's analagous to you claiming someone is a murderer because an astrologer told you so.  Then when I question whether an astrologer is really valid evidence you claim that my argument just ignores any evidence contrary to my belief.  No.  I'm just saying you've reached an invalid conclusion because an astrologer is not valid evidence.

I question your motives in this as all you appear to be doing is just arguing for the sake of it without actually having anything useful to add to the discussion if you can't even be bothered to put up a proper a counter view.

It's no better than someone shouting out in a discussion I disagree and then if asked why they disagree rather than giving a valid reason they just walk off.
Title: Re: Boyajians Star Updates And Discussion
Post by: ChrisWilson68 on 07/08/2017 11:42 PM
Other than the fact your misrepresenting the argument regarding the possible evidence I was referring to which is from the photographic plates examined covering many years in time for the long term dimming trend.

You must be misunderstanding my argument because for my argument it's irrelevant where the evidence is coming from or what the timescale is.  My argument is that even if we accept that there is a dimming trend, on any timescale, it's not justified to assume that dimming trend will continue to zero.  It doesn't matter if the timescale is 2 days or 600 days or 150 years.  It also doesn't matter if the dimming is by 0.5% or 50%.  If you think any of those things matter to my argument, you're not understanding my argument.

At least on my side of the discussion I have some basis in data, something that you don't have. You seem to have come up with an argument that just ignores any evidence contrary to your belief.

Not true in the slightest.  I'm just questioning your evidence.  It's valid to question someone else's conclusions without presenting evidence to the contrary if the argument is that the evidence that other person presented is not valid.

It's analagous to you claiming someone is a murderer because an astrologer told you so.  Then when I question whether an astrologer is really valid evidence you claim that my argument just ignores any evidence contrary to my belief.  No.  I'm just saying you've reached an invalid conclusion because an astrologer is not valid evidence.

I question your motives in this as all you appear to be doing is just arguing for the sake of it without actually having anything useful to add to the discussion. If you can't even be bothered to put up a proper a counter view then it's little better than trolling.

That's not fair at all.  My motives are pure.  It's perfectly valid to question someone else's bogus conclusions without offering an alternative conclusion.  It does add something very useful to the discussion: it points out an error in what someone else is claiming.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/08/2017 11:54 PM
Other than the fact your misrepresenting the argument regarding the possible evidence I was referring to which is from the photographic plates examined covering many years in time for the long term dimming trend.

You must be misunderstanding my argument because for my argument it's irrelevant where the evidence is coming from or what the timescale is.  My argument is that even if we accept that there is a dimming trend, on any timescale, it's not justified to assume that dimming trend will continue to zero.  It doesn't matter if the timescale is 2 days or 600 days or 150 years.  It also doesn't matter if the dimming is by 0.5% or 50%.  If you think any of those things matter to my argument, you're not understanding my argument.

At least on my side of the discussion I have some basis in data, something that you don't have. You seem to have come up with an argument that just ignores any evidence contrary to your belief.

Not true in the slightest.  I'm just questioning your evidence.  It's valid to question someone else's conclusions without presenting evidence to the contrary if the argument is that the evidence that other person presented is not valid.

It's analagous to you claiming someone is a murderer because an astrologer told you so.  Then when I question whether an astrologer is really valid evidence you claim that my argument just ignores any evidence contrary to my belief.  No.  I'm just saying you've reached an invalid conclusion because an astrologer is not valid evidence.

I question your motives in this as all you appear to be doing is just arguing for the sake of it without actually having anything useful to add to the discussion. If you can't even be bothered to put up a proper a counter view then it's little better than trolling.

That's not fair at all.  My motives are pure.  It's perfectly valid to question someone else's bogus conclusions without offering an alternative conclusion.  It does add something very useful to the discussion: it points out an error in what someone else is claiming.

How is bogus when I am just putting the viewpoint that some data that has been produced by an expert in his field suggests there is a long term dimming trend. The fact that you see fit to make the vaguely insulting comparison to the use of an astrologer in a murder trial is what makes me question your motives in this. I am not insulted on my behalf but rather that you would even suggest that kind of comparison when you know very well that gentleman who did the photographic analysis that suggested the long term dimming is hardly a charlatan to be compared with an astrologer.
Title: Re: Boyajians Star Updates And Discussion
Post by: ChrisWilson68 on 07/09/2017 12:53 AM
It seems pointless to me to continue this back and forth.  Lets just both agree that we could continue and never agree.  I continue to believe that you are not understanding what I am saying.   And I don't think anyone else reading this wants to read any more of it.

So, I won't respond to the specifics of your latest reply.  Instead, I'll just say I don't agree, and stipulate that I'm sure you don't agree with my not agreeing and be done with it.

Title: Re: Boyajians Star Updates And Discussion
Post by: moreno7798 on 07/09/2017 02:27 PM
Other than the fact your misrepresenting the argument regarding the possible evidence I was referring to which is from the photographic plates examined covering many years in time for the long term dimming trend.

You must be misunderstanding my argument because for my argument it's irrelevant where the evidence is coming from or what the timescale is.  My argument is that even if we accept that there is a dimming trend, on any timescale, it's not justified to assume that dimming trend will continue to zero.  It doesn't matter if the timescale is 2 days or 600 days or 150 years.  It also doesn't matter if the dimming is by 0.5% or 50%.  If you think any of those things matter to my argument, you're not understanding my argument.

Chris, according to your argument then Moore's Law is just dust in the wind. Anyone could throw a wrench into any theory with the "Who knows what the future holds?" argument. Data is paramount.

I probably don't need to tell you why trends and predictability have been extremely successful methods in science. I understand your argument that right now there's no way to know how this mystery will turn out - especially a century from now - But may I suggest to you that "we should follow the data" and the data suggests a trend - a trend that stared a century ago and continues. So yeah, Follow the data.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/09/2017 02:36 PM
Other than the fact your misrepresenting the argument regarding the possible evidence I was referring to which is from the photographic plates examined covering many years in time for the long term dimming trend.

You must be misunderstanding my argument because for my argument it's irrelevant where the evidence is coming from or what the timescale is.  My argument is that even if we accept that there is a dimming trend, on any timescale, it's not justified to assume that dimming trend will continue to zero.  It doesn't matter if the timescale is 2 days or 600 days or 150 years.  It also doesn't matter if the dimming is by 0.5% or 50%.  If you think any of those things matter to my argument, you're not understanding my argument.

Chris, according to your argument then Moore's Law is just dust in the wind. Anyone could throw a wrench into any theory with the "Who knows what the future holds?" argument. Data is paramount.

I probably don't need to tell you why trends and predictability have been extremely successful methods in science. I understand your argument that right now there's no way to know how this mystery will turn out - especially a century from now - But may I suggest to you that "we should follow the data" and the data suggests a trend - a trend that stared a century ago and continues. So yeah, Follow the data.

Thank you for getting across what I was obviously failing to do.
Title: Re: Boyajians Star Updates And Discussion
Post by: meekGee on 07/09/2017 04:57 PM
Seems like this star is now dimming at an accelerating rate. That doesn't seem like something that would fit with dust but rather the star itself.

Could I be so bold as to suggest that perhaps we're looking at the death of a star. As we have been shown time and again, the universe never fails to surprise us. Perhaps "SOME" stars do not die slowly (billions of years) through the usual process of exhaustion of nuclear fusion. Maybe . . .just maybe some stars have "sudden Deaths" (perhaps in the thousands of years as opposed to billions).

It's possible we're witnessing the star equivalent of a human heart attack. Stars may be much more unpredictable than we ever thought.

Just a thought.

I'd slow down there.

Both these posts attribute "intent" to data.

They're assuming "inertia" to the dimming and extrapolate forward, even going as far as suggesting some sort of stellar collapse  (sudden stellar collapse syndrome?).

But you're supposed to try to fit data to a model, not to a conclusion.

If you haven't, then the data is not supporting your conclusion.

For example, the temperature around my house went up last night, and the average temperature has been increasing for the last 3 months.  This does not mean the earth is melting.

Tracking global temperatures change is an even better razor.  If there wasn't a meteorological model behind it (greenhouse gasses), then just the global temperature rise would not be a good indicator for things to come.  (You can argue the model, but the point is that there IS one.)

We're seeing the light from a star behave in an unexplained way.  So far, we don't have a model that fits.  Lacking a model, all we can do is try to come up with one.
Title: Re: Boyajians Star Updates And Discussion
Post by: TakeOff on 07/09/2017 05:19 PM
What has spectroscopy to say about this new dimming? I suppose that its spectrum is being observed continuously now.

Seems like this star is now dimming at an accelerating rate. That doesn't seem like something that would fit with dust but rather the star itself.

Could I be so bold as to suggest that perhaps we're looking at the death of a star. As we have been shown time and again, the universe never fails to surprise us. Perhaps "SOME" stars do not die slowly (billions of years) through the usual process of exhaustion of nuclear fusion. Maybe . . .just maybe some stars have "sudden Deaths" (perhaps in the thousands of years as opposed to billions).

It's possible we're witnessing the star equivalent of a human heart attack. Stars may be much more unpredictable than we ever thought.

Just a thought.

I'd slow down there.

Both these posts attribute "intent" to data.

They're assuming "inertia" to the dimming and extrapolate forward, even going as far as suggesting some sort of stellar collapse  (sudden stellar collapse syndrome?).
I think that the only intent was to explain in a non-technical way where the fitted (tiny part of) the curve crosses the X-axis. Since it doesn't have constant slope.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/09/2017 05:27 PM
What has spectroscopy to say about this new dimming? I suppose that its spectrum is being observed continuously now.

Seems like this star is now dimming at an accelerating rate. That doesn't seem like something that would fit with dust but rather the star itself.

Could I be so bold as to suggest that perhaps we're looking at the death of a star. As we have been shown time and again, the universe never fails to surprise us. Perhaps "SOME" stars do not die slowly (billions of years) through the usual process of exhaustion of nuclear fusion. Maybe . . .just maybe some stars have "sudden Deaths" (perhaps in the thousands of years as opposed to billions).

It's possible we're witnessing the star equivalent of a human heart attack. Stars may be much more unpredictable than we ever thought.

Just a thought.

I'd slow down there.

Both these posts attribute "intent" to data.

They're assuming "inertia" to the dimming and extrapolate forward, even going as far as suggesting some sort of stellar collapse  (sudden stellar collapse syndrome?).
I think that the only intent was to explain in a non-technical way where the fitted (tiny part of) the curve crosses the X-axis. Since it doesn't have constant slope.

I hold my hands up a bit here because I think what's caused the confusion partly is my ill advised idea to repeat the claim in that last video I posted of accelerating dimming. I really shouldn't repeat other people's assumptions. So I apologise over that but I do stand by the idea of the star suffering long term dimming, as that's a better supported proposition.
Title: Re: Boyajians Star Updates And Discussion
Post by: ChrisWilson68 on 07/09/2017 05:48 PM
Other than the fact your misrepresenting the argument regarding the possible evidence I was referring to which is from the photographic plates examined covering many years in time for the long term dimming trend.

You must be misunderstanding my argument because for my argument it's irrelevant where the evidence is coming from or what the timescale is.  My argument is that even if we accept that there is a dimming trend, on any timescale, it's not justified to assume that dimming trend will continue to zero.  It doesn't matter if the timescale is 2 days or 600 days or 150 years.  It also doesn't matter if the dimming is by 0.5% or 50%.  If you think any of those things matter to my argument, you're not understanding my argument.

Chris, according to your argument then Moore's Law is just dust in the wind. Anyone could throw a wrench into any theory with the "Who knows what the future holds?" argument. Data is paramount.

I probably don't need to tell you why trends and predictability have been extremely successful methods in science. I understand your argument that right now there's no way to know how this mystery will turn out - especially a century from now - But may I suggest to you that "we should follow the data" and the data suggests a trend - a trend that stared a century ago and continues. So yeah, Follow the data.

No, you, also, don't understand my argument.

Let's take Moore's Law.  My argument isn't that Moore's Law is "dust in the wind".  My argument isn't that seeing trends is meaningless.  My argument is that trends don't necessarily last forever.  So a conclusion based on an assumption that a trend has to last forever is not a valid conclusion.

Moore's Law isn't going to last forever.  If it did, we'd have transistors smaller than atoms in the not-too-distant future.

With Moore's Law, we understand very well the underlying reasons for the trend, and so we have some good ideas about the boundaries it will run up against.  It is already running up against those boundaries -- it is slowing down.

With the long-term dimming of Tabby's Star, we don't understand the underlying mechanism, so we can't possibly know where the long-term dimming will end.  So, it's really, really foolish to say it's not dust because dust wouldn't lead to 100% dimming and the long-term dimming trend is going to go to 100% dimming.

That is my argument, and that's what it's been all along: ruling out dust as a cause of the dimming on an assumption that a dimming trend will go to 100% dimming is foolish.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/09/2017 06:32 PM
Other than the fact your misrepresenting the argument regarding the possible evidence I was referring to which is from the photographic plates examined covering many years in time for the long term dimming trend.

You must be misunderstanding my argument because for my argument it's irrelevant where the evidence is coming from or what the timescale is.  My argument is that even if we accept that there is a dimming trend, on any timescale, it's not justified to assume that dimming trend will continue to zero.  It doesn't matter if the timescale is 2 days or 600 days or 150 years.  It also doesn't matter if the dimming is by 0.5% or 50%.  If you think any of those things matter to my argument, you're not understanding my argument.

Chris, according to your argument then Moore's Law is just dust in the wind. Anyone could throw a wrench into any theory with the "Who knows what the future holds?" argument. Data is paramount.

I probably don't need to tell you why trends and predictability have been extremely successful methods in science. I understand your argument that right now there's no way to know how this mystery will turn out - especially a century from now - But may I suggest to you that "we should follow the data" and the data suggests a trend - a trend that stared a century ago and continues. So yeah, Follow the data.

No, you, also, don't understand my argument.

Let's take Moore's Law.  My argument isn't that Moore's Law is "dust in the wind".  My argument isn't that seeing trends is meaningless.  My argument is that trends don't necessarily last forever.  So a conclusion based on an assumption that a trend has to last forever is not a valid conclusion.

Moore's Law isn't going to last forever.  If it did, we'd have transistors smaller than atoms in the not-too-distant future.

With Moore's Law, we understand very well the underlying reasons for the trend, and so we have some good ideas about the boundaries it will run up against.  It is already running up against those boundaries -- it is slowing down.

With the long-term dimming of Tabby's Star, we don't understand the underlying mechanism, so we can't possibly know where the long-term dimming will end.  So, it's really, really foolish to say it's not dust because dust wouldn't lead to 100% dimming and the long-term dimming trend is going to go to 100% dimming.

That is my argument, and that's what it's been all along: ruling out dust as a cause of the dimming on an assumption that a dimming trend will go to 100% dimming is foolish.

So is you assuming it definitely is dust, this is the part of your argument that I disagree with as there is insufficient data at this time to support the idea it definitely is dust.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/09/2017 06:36 PM
Today's update. Things look pretty flat with the star. OCG stable, TFN down slightly.

http://www.wherestheflux.com/single-post/2017/07/09/Dip-update-28n---Sunday-Scoop
Title: Re: Boyajians Star Updates And Discussion
Post by: ChrisWilson68 on 07/09/2017 06:40 PM
Other than the fact your misrepresenting the argument regarding the possible evidence I was referring to which is from the photographic plates examined covering many years in time for the long term dimming trend.

You must be misunderstanding my argument because for my argument it's irrelevant where the evidence is coming from or what the timescale is.  My argument is that even if we accept that there is a dimming trend, on any timescale, it's not justified to assume that dimming trend will continue to zero.  It doesn't matter if the timescale is 2 days or 600 days or 150 years.  It also doesn't matter if the dimming is by 0.5% or 50%.  If you think any of those things matter to my argument, you're not understanding my argument.

Chris, according to your argument then Moore's Law is just dust in the wind. Anyone could throw a wrench into any theory with the "Who knows what the future holds?" argument. Data is paramount.

I probably don't need to tell you why trends and predictability have been extremely successful methods in science. I understand your argument that right now there's no way to know how this mystery will turn out - especially a century from now - But may I suggest to you that "we should follow the data" and the data suggests a trend - a trend that stared a century ago and continues. So yeah, Follow the data.

No, you, also, don't understand my argument.

Let's take Moore's Law.  My argument isn't that Moore's Law is "dust in the wind".  My argument isn't that seeing trends is meaningless.  My argument is that trends don't necessarily last forever.  So a conclusion based on an assumption that a trend has to last forever is not a valid conclusion.

Moore's Law isn't going to last forever.  If it did, we'd have transistors smaller than atoms in the not-too-distant future.

With Moore's Law, we understand very well the underlying reasons for the trend, and so we have some good ideas about the boundaries it will run up against.  It is already running up against those boundaries -- it is slowing down.

With the long-term dimming of Tabby's Star, we don't understand the underlying mechanism, so we can't possibly know where the long-term dimming will end.  So, it's really, really foolish to say it's not dust because dust wouldn't lead to 100% dimming and the long-term dimming trend is going to go to 100% dimming.

That is my argument, and that's what it's been all along: ruling out dust as a cause of the dimming on an assumption that a dimming trend will go to 100% dimming is foolish.

So is you assuming it definitely is dust, this is the part of your argument that I disagree with as there is insufficient data at this time to support the idea it definitely is dust.

No.  For the billionth time.  That's not what I said.

I am not assuming it is or isn't dust.  I'm saying your argument that it can't be dust is not a valid argument.

If you're finally coming around to saying there's insufficient data at this time, great!  That's what I've been saying all along.

Let's not forget your post that started this whole back-and-forth:

Seems like this star is now dimming at an accelerating rate. That doesn't seem like something that would fit with dust but rather the star itself.

All I've ever said is that we don't know.  It could still be dust.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/09/2017 06:43 PM
Other than the fact your misrepresenting the argument regarding the possible evidence I was referring to which is from the photographic plates examined covering many years in time for the long term dimming trend.

You must be misunderstanding my argument because for my argument it's irrelevant where the evidence is coming from or what the timescale is.  My argument is that even if we accept that there is a dimming trend, on any timescale, it's not justified to assume that dimming trend will continue to zero.  It doesn't matter if the timescale is 2 days or 600 days or 150 years.  It also doesn't matter if the dimming is by 0.5% or 50%.  If you think any of those things matter to my argument, you're not understanding my argument.

Chris, according to your argument then Moore's Law is just dust in the wind. Anyone could throw a wrench into any theory with the "Who knows what the future holds?" argument. Data is paramount.

I probably don't need to tell you why trends and predictability have been extremely successful methods in science. I understand your argument that right now there's no way to know how this mystery will turn out - especially a century from now - But may I suggest to you that "we should follow the data" and the data suggests a trend - a trend that stared a century ago and continues. So yeah, Follow the data.

No, you, also, don't understand my argument.

Let's take Moore's Law.  My argument isn't that Moore's Law is "dust in the wind".  My argument isn't that seeing trends is meaningless.  My argument is that trends don't necessarily last forever.  So a conclusion based on an assumption that a trend has to last forever is not a valid conclusion.

Moore's Law isn't going to last forever.  If it did, we'd have transistors smaller than atoms in the not-too-distant future.

With Moore's Law, we understand very well the underlying reasons for the trend, and so we have some good ideas about the boundaries it will run up against.  It is already running up against those boundaries -- it is slowing down.

With the long-term dimming of Tabby's Star, we don't understand the underlying mechanism, so we can't possibly know where the long-term dimming will end.  So, it's really, really foolish to say it's not dust because dust wouldn't lead to 100% dimming and the long-term dimming trend is going to go to 100% dimming.

That is my argument, and that's what it's been all along: ruling out dust as a cause of the dimming on an assumption that a dimming trend will go to 100% dimming is foolish.

So is you assuming it definitely is dust, this is the part of your argument that I disagree with as there is insufficient data at this time to support the idea it definitely is dust.

No.  For the billionth time.  That's not what I said.

I am not assuming it is or isn't dust.  I'm saying your argument that it can't be dust is not a valid argument.

If you're finally coming around to saying there's insufficient data at this time, great!  That's what I've been saying all along.

Let's not forget your post that started this whole back-and-forth:

Seems like this star is now dimming at an accelerating rate. That doesn't seem like something that would fit with dust but rather the star itself.

All I've ever said is that we don't know.  It could still be dust.

If you did say that it was completely unclear to me because otherwise I wouldn't have questioned you on it. As for the accelerating dimming I've already addressed that claim with a post today upthread.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/09/2017 08:53 PM
Quote
John Wenz @johnwenz
·
8 Jul

Are Elsie and Celeste seemingly two different objects and / or stellar activities?

Tabetha Boyajian @tsboyajian

Replying to @johnwenz
Almost certainly

https://mobile.twitter.com/tsboyajian/status/884026977845489664
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/09/2017 10:39 PM
https://www.youtube.com/watch?v=nUmTXjFvwL0
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/10/2017 07:33 PM
Quote
Hi everyone,
 
We have been at a steady 0.5% depressed for a week now.
 
More later!
 
~Tabby and team

http://www.wherestheflux.com/single-post/2017/07/10/Dip-update-29n
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/12/2017 03:45 PM
Quote
Hi everyone,
 
Sorry for missing yesterday's update, it was my daughters 6th birthday :)
 
Here is the latest from LCO.  Yesterday there was only data taken at TFN (not OGG). The most recent OGG data here are preliminary because the station is still taking data at the time of this post.   
 
The flux remains constant for the past 10 days at 99.5%. Wow - always full of surprises!
 
~Tabby and team

http://www.wherestheflux.com/single-post/2017/07/12/Dip-update-30n---the-new-normal
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/12/2017 03:51 PM
After a couple of V shaped dips this looks more like a U. That makes it look far more like a typical planetary transit rather than dust. At 0.5% that seems easily in the range of a gas giant.
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 07/12/2017 04:13 PM
The last 10 days or so of flux days looks to be the most consistent series of measurements in the entire dataset.  I'm really looking forward to commentary from J. Wright and other experts regarding how this data either fits or eliminates any of the plausible candidate scenarios put forth in previous studies.   To me,  ISM looks less and less likely,  but not enough new data to support any alternate theories.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/12/2017 04:40 PM
The last 10 days or so of flux days looks to be the most consistent series of measurements in the entire dataset.  I'm really looking forward to commentary from J. Wright and other experts regarding how this data either fits or eliminates any of the plausible candidate scenarios put forth in previous studies.   To me,  ISM looks less and less likely,  but not enough new data to support any alternate theories.

Would you say it's reasonable for me to state that the most recent dip does have the hallmarks of being a planetary transit? Not saying it definitely is just that it has the hallmarks.

As an aside I was intrigued by the Professor's comment that the first two dips looked to be different 'whatever's'.
Title: Re: Boyajians Star Updates And Discussion
Post by: Orbiter on 07/12/2017 04:56 PM
Looks more like a slow moving transit of a planet than dust.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/12/2017 05:19 PM
Looks more like a slow moving transit of a planet than dust.

Agree. Must be in a orbit over a thousand years.
Title: Re: Boyajians Star Updates And Discussion
Post by: Mongo62 on 07/12/2017 06:11 PM
A while ago, I made a plot with the measured survey brightnesses of this star from the late 19th century to the 1970s. There was a lot of random scatter, but to me the plot looked like a staircase pattern, with the star's measured brightnesses mostly level but with occasional sudden drops to a new plateau.

Could this have happened here? A sudden drop to a new standard brightness (as observed from here)? If so, it might be significant that it happened during a series of brightness dips.

Time will tell. It will be interesting if the star's brightness is still at .995 the previous standard a month from now.
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 07/12/2017 09:31 PM
After a couple of V shaped dips this looks more like a U. That makes it look far more like a typical planetary transit rather than dust. At 0.5% that seems easily in the range of a gas giant.
Given all the varied dips observed, this doesn't seem like a strong argument for a transit.
Agree. Must be in a orbit over a thousand years.
The odds of seeing such planet transit are really, really bad. Not only does it only happen once every thousand years, the geometric probability goes down as as the orbit gets larger.

Mongo62's suggestion of the long term dimming happening in steps is interesting. No idea what kind of mechanism would be behind that, but it would certainly be a big clue if it turned out to be true.

Dr. Boyajian did mention that they expected to get a paper out about the May dip relatively soon, which will hopefully narrow the possible solutions a bit... or at least add new food for speculation ;D
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/12/2017 09:52 PM
After a couple of V shaped dips this looks more like a U. That makes it look far more like a typical planetary transit rather than dust. At 0.5% that seems easily in the range of a gas giant.
Given all the varied dips observed, this doesn't seem like a strong argument for a transit.
Agree. Must be in a orbit over a thousand years.
The odds of seeing such planet transit are really, really bad. Not only does it only happen once every thousand years, the geometric probability goes down as as the orbit gets larger.

Mongo62's suggestion of the long term dimming happening in steps is interesting. No idea what kind of mechanism would be behind that, but it would certainly be a big clue if it turned out to be true.

Dr. Boyajian did mention that they expected to get a paper out about the May dip relatively soon, which will hopefully narrow the possible solutions a bit... or at least add new food for speculation ;D

I don't think it will being as they seem to believe different 'things' cause different dips. Just because dust might have caused one doesn't follow it caused the others.

Also there seems to be some goalpost shifting going on here as you claim it's unlikely to be a planet because that would be such a rare coincidence. Yet when I made an argument up thread about a possible theory I was told an argument against what I was suggesting was just because something was a rare coincidence doesn't mean we might not see it. You can't have an argument both ways when it suits you.
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 07/12/2017 09:54 PM
The last 10 days or so of flux days looks to be the most consistent series of measurements in the entire dataset.  I'm really looking forward to commentary from J. Wright and other experts regarding how this data either fits or eliminates any of the plausible candidate scenarios put forth in previous studies.   To me,  ISM looks less and less likely,  but not enough new data to support any alternate theories.

Would you say it's reasonable for me to state that the most recent dip does have the hallmarks of being a planetary transit? Not saying it definitely is just that it has the hallmarks.

As an aside I was intrigued by the Professor's comment that the first two dips looked to be different 'whatever's'.
.
As a single event, the latest "U" shaped dip does look like a planet.  But as noted, the periodicity would be very long , and improbable to capture.   A long period planet seems to do little to explain the greater Kepler dimming, or the Long term dimming noted by Schaefer,  and supported by additional review of the Kepler dataset.   J. Wright correctly pointed out that whatever is responsible for the dimming needs to explain all the observations, not just a single observation.  Something about the invocation of too many unicorns...
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/12/2017 09:58 PM
The last 10 days or so of flux days looks to be the most consistent series of measurements in the entire dataset.  I'm really looking forward to commentary from J. Wright and other experts regarding how this data either fits or eliminates any of the plausible candidate scenarios put forth in previous studies.   To me,  ISM looks less and less likely,  but not enough new data to support any alternate theories.

Would you say it's reasonable for me to state that the most recent dip does have the hallmarks of being a planetary transit? Not saying it definitely is just that it has the hallmarks.

As an aside I was intrigued by the Professor's comment that the first two dips looked to be different 'whatever's'.
.
As a single event, the latest "U" shaped dip does look like a planet.  But as noted, the periodicity would be very long , and improbable to capture.   A long period planet seems to do little to explain the greater Kepler dimming, or the Long term dimming noted by Schaefer,  and supported by additional review of the Kepler dataset.   J. Wright correctly pointed out that whatever is responsible for the dimming needs to explain all the observations, not just a single observation.  Something about the invocation of too many unicorns...

I think that's a red herring here as just because we might have detected a planet it may just be a coincidence because we happen to be it observing it so much. It doesn't automatically have to be invoked to explain anything else other than we just happened to find that a star has a planet. I don't see any reason why this star shouldn't have planets.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/12/2017 10:37 PM
Bruce Gary compares his observations against LCGO & they aren't all that inconsistent with each other.

http://www.brucegary.net/ts/
Title: Re: Boyajians Star Updates And Discussion
Post by: Mongo62 on 07/13/2017 02:41 AM
Fredric Parker July 12 update:

https://www.youtube.com/watch?v=bSlYbuATuyA
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 07/13/2017 02:52 AM
I don't think it will being as they seem to believe different 'things' cause different dips. Just because dust might have caused one doesn't follow it caused the others.
If you are referring to https://mobile.twitter.com/tsboyajian/status/884026977845489664 I think you have misunderstood. I believe she's just saying they would be different objects (if the dips are in fact caused by specific objects), not totally different underlying phenomena.

Occam's razor suggests that all of the various weird things this star does are more likely to be connected than totally independent.

Quote
Yet when I made an argument up thread about a possible theory I was told an argument against what I was suggesting was just because something was a rare coincidence doesn't mean we might not see it. You can't have an argument both ways when it suits you.
No, it depends on how unlikely the event: If the explanation is something that 1/100,000 of stars do most of the time (or most stars do 1/100,000th the time, or something in between) seeing one in the Kepler field is completely reasonable. If the odds are 1 in a billion, not so much.

I'm not going to do the math (see http://certificate.ulo.ucl.ac.uk/modules/year_one/NASA_Kepler/character.html if you want) but catching a planet in a 1000 year orbit with a few years of observation is pretty unlikely.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/13/2017 06:24 AM
I don't think it will being as they seem to believe different 'things' cause different dips. Just because dust might have caused one doesn't follow it caused the others.
If you are referring to https://mobile.twitter.com/tsboyajian/status/884026977845489664 I think you have misunderstood. I believe she's just saying they would be different objects (if the dips are in fact caused by specific objects), not totally different underlying phenomena.

Occam's razor suggests that all of the various weird things this star does are more likely to be connected than totally independent.

Quote
Yet when I made an argument up thread about a possible theory I was told an argument against what I was suggesting was just because something was a rare coincidence doesn't mean we might not see it. You can't have an argument both ways when it suits you.
No, it depends on how unlikely the event: If the explanation is something that 1/100,000 of stars do most of the time (or most stars do 1/100,000th the time, or something in between) seeing one in the Kepler field is completely reasonable. If the odds are 1 in a billion, not so much.

I'm not going to do the math (see http://certificate.ulo.ucl.ac.uk/modules/year_one/NASA_Kepler/character.html if you want) but catching a planet in a 1000 year orbit with a few years of observation is pretty unlikely.
But that doesn't make it impossible though. The possibility of just so happening to catch a planet in a long orbit cannot be completely dismissed.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/13/2017 02:54 PM
Latest update and it looks like we are stuck where we are.

http://www.wherestheflux.com/single-post/2017/07/13/Dip-update-31n
Title: Re: Boyajians Star Updates And Discussion
Post by: Cinder on 07/14/2017 12:34 AM
I don't think it will being as they seem to believe different 'things' cause different dips. Just because dust might have caused one doesn't follow it caused the others.
If you are referring to https://mobile.twitter.com/tsboyajian/status/884026977845489664 I think you have misunderstood. I believe she's just saying they would be different objects (if the dips are in fact caused by specific objects), not totally different underlying phenomena.

Occam's razor suggests that all of the various weird things this star does are more likely to be connected than totally independent.

Quote
Yet when I made an argument up thread about a possible theory I was told an argument against what I was suggesting was just because something was a rare coincidence doesn't mean we might not see it. You can't have an argument both ways when it suits you.
No, it depends on how unlikely the event: If the explanation is something that 1/100,000 of stars do most of the time (or most stars do 1/100,000th the time, or something in between) seeing one in the Kepler field is completely reasonable. If the odds are 1 in a billion, not so much.

I'm not going to do the math (see http://certificate.ulo.ucl.ac.uk/modules/year_one/NASA_Kepler/character.html if you want) but catching a planet in a 1000 year orbit with a few years of observation is pretty unlikely.
But that doesn't make it impossible though. The possibility of just so happening to catch a planet in a long orbit cannot be completely dismissed.
Ceteris paribus, that conjecture is still lower in probability than the other conjectures.  Whether or not one puts it below or above dismissal "cutoff".
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 07/14/2017 07:11 AM
Question.

If the star has been long term dimming, what is the 100% flux level they are using as the benchmark? The latest updates show 99.5% flux or thereabouts, but what is that measured against? The flux when Kepler first started observing the star? The flux from May? Because presumably this benchmark level should have been steadily declining, if the star is gradually dimming.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/14/2017 08:05 AM
Question.

If the star has been long term dimming, what is the 100% flux level they are using as the benchmark? The latest updates show 99.5% flux or thereabouts, but what is that measured against? The flux when Kepler first started observing the star? The flux from May? Because presumably this benchmark level should have been steadily declining, if the star is gradually dimming.

You're not the first to ask this question and I can only say that this seems to vary on who the observer is. In the case of Professor Boyajian's team I confess I don't know how they've worked this out. I am sure someone will know though.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/14/2017 07:13 PM
Another day another update.

http://www.wherestheflux.com/single-post/2017/07/14/Dip-update-32n
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/16/2017 12:12 AM
https://www.youtube.com/watch?v=ANSFcswnyAM

Plus another update with the star remaining steady at its current level.

http://www.wherestheflux.com/single-post/2017/07/15/Dip-update-33n
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/17/2017 08:00 AM
Quote
Tabetha Boyajian @tsboyajian

Downloaded new data just before wifi fail (so no blog post today). here are the latest #TabbysStar obs

https://mobile.twitter.com/tsboyajian/status/886634761917214720
Title: Re: Boyajians Star Updates And Discussion
Post by: TakeOff on 07/17/2017 11:45 AM
About the 15 July report. Flux looks pretty constant (with a 100 days gap) before day 500 after which it gets lower. But after day 600 the overwhelming majority of observation s are above the fitted curve. Is it really warranted to fit one decreasing curve over the entire period? There's no astrophysical model motivating fitting this particular "functional form" of smooth dimming.
Title: Re: Boyajians Star Updates And Discussion
Post by: high road on 07/17/2017 12:21 PM
About the 15 July report. Flux looks pretty constant (with a 100 days gap) before day 500 after which it gets lower. But after day 600 the overwhelming majority of observation s are above the fitted curve. Is it really warranted to fit one decreasing curve over the entire period? There's no astrophysical model motivating fitting this particular "functional form" of smooth dimming.

The fact that no astrophysical model fits the data is what makes this star so intriguing.

They've been trying to predict the star's behaviour. That's all they're doing now too. If it follows this curve, we need to find out why, meaning creating a new astrophysical model based on the observations. If it doesn't, one more prediction tested and disproved. Excellent points for falsifiability.

Ticking off the wrong theories one by one is a great and exciting way to do science. I love being able to follow this up so closely.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/17/2017 10:35 PM
Quote
Hi everyone,
 
Below is the graph with today's update. 
 
Note: on June 26 (~45 on the x-axis) and after, there have been two 40cm telescopes at each of the LCO stations (OGG and TFN) taking observations of our star (instead of one at each station).  Previously posted light curves were generated without this data taken from the second set of telescopes. However, we have now collected enough data to verify that there is consistency with the two new telescopes compared to the ones that we have been using.  So the light curve below now includes the "new", old data, combined with the data set that you are accustomed to seeing.   
 
The most recent data (there has been bad weather at OGG) look to be fairly consistent with normal brightness (i.e., the error bars on the two, right-most, blue points touch the dotted horizontal line at 1.0). This seems to indicate that the ~2 week long, 0.5% dip is nearing its end.  However, given the unpredictable nature of this object, I hesitate to make that official call just yet. Im also torn on whether we should christen these small 0.5% dips, or save the names for just the bigger ones. We'll have to make a decision on this before too long though!     
 
Lastly, we continue to work on the Elsie detection paper.  Alas, these things (science in general) always take longer than expected.  I hope it is not terribly discouraging to you, and I promise that you will be the first to hear when things finalize.
 
~Tabby and team

http://www.wherestheflux.com/single-post/2017/07/17/Dip-update-34n
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/19/2017 12:26 AM
https://www.youtube.com/watch?v=KvEM1zI3VxI
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/20/2017 05:46 PM
This 0.5% dip seems to be a unique feature especially for the length of time it's lasting, as I don't remember seeing anything like it in the Kepler data.

Quote
[Orig: July, 20 2017]
 
Hi everyone,
 
Below is the newest light curve.  Again, the weather was bad at OGG, but observations at TFN continue.  I had previously commented that the two TFN observations ~70 on the x-axis could indicate a return to normal (the error bars crossing the dotted line at 1.0).  However, perhaps this was a premature conclusion, as they are also in agreement with the 0.5% flux decrement over the past few weeks (note that compared to other measurements, the error bars on these points are somewhat larger). 
 
Got to run for now, more later!     
 
~Tabby and team

http://www.wherestheflux.com/single-post/2017/07/20/Dip-update-37n
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/21/2017 07:36 PM
And still the star stays low.

https://mobile.twitter.com/tsboyajian/status/888456946977841152
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/21/2017 10:19 PM
https://www.youtube.com/watch?v=RTj44MvYki8
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/23/2017 06:58 PM
Still depressed at the same level, three weeks now.

Quote
[Orig: July, 23 2017]
 
Hi everyone,
 
Excuse the break in frequent posts, Ive been traveling.  I also forgot to hit "publish" for the last update (38/n), so this is the updated post with the newest light curve as of 2 hours ago. 
 
More later!
 
 
~Tabby and team

http://www.wherestheflux.com/single-post/2017/07/23/Dip-update-38an
Title: Re: Boyajians Star Updates And Discussion
Post by: Mongo62 on 07/23/2017 11:34 PM
https://www.youtube.com/watch?v=T-dm2-WNvvs
Title: Re: Boyajians Star Updates And Discussion
Post by: meekGee on 07/24/2017 04:25 AM
I just watched those clips for the first time.

If I'm following correctly, then I don't agree with the methodology.   He's discounting short dips as mere "transients" that should be ignore, but looking at a somewhat longer-term decrease and inferring from it a "longer term accelerated dimming".  So basically extrapolating the second derivative.

That's a giant leap in logic.

Especially since on the 600 day view (two clips up) it's apparent that there are only two clusters of data points, so really statistically all we have is that the flux today, if you low-pass the shorter "weekish" events, is lower than it was some 300 days ago.

There is no reason to think that this is part of downward trend, and doubly no reason to think that this is part of an accelerating downward trend.

And I wish the videos were not anonymous but rather attributed to someone.  "That's all we have for you today" - who's "we"?
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/24/2017 05:46 AM
They aren't anonymous as they are all posted on his channel, him being Fredric Parker.

I didn't post that last video myself as though I did see the video, it was mostly concerned with promoting his own theory which I don't agree with.
Title: Re: Boyajians Star Updates And Discussion
Post by: high road on 07/24/2017 10:35 AM
I agree it's too early to conclude there's a clear trend without cherrypicking the desired points. Considering the last measurements seem to have stabilized, I hope this week we'll see whether the star returns back towards normal, stays at a current level, or continues to dim.

However, should the measurements follow the 'accelerated dimming' graph, how long would it take for that hypothesis (or does the inferred formula make it a theory?) to be credible enough to warrant time on the bigger telescopes for a detailed study over many wavelengths to see if there's more dimming in certain wavelengths?

The previous request was rejected because Tabby's team was unable to specify the specific time of the measurements. If a new proposal would ask to take measurements now, and again in six months for comparison, that might be specific enough to be accepted.

Considering we're probably in for the long haul, does anyone know if there's a limit on how long the two observatories can take measurements with the available funding? Or was the funding required for Tabby's team and not for time on these two telescopes?
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/24/2017 01:01 PM
I agree it's too early to conclude there's a clear trend without cherrypicking the desired points. Considering the last measurements seem to have stabilized, I hope this week we'll see whether the star returns back towards normal, stays at a current level, or continues to dim.

However, should the measurements follow the 'accelerated dimming' graph, how long would it take for that hypothesis (or does the inferred formula make it a theory?) to be credible enough to warrant time on the bigger telescopes for a detailed study over many wavelengths to see if there's more dimming in certain wavelengths?

The previous request was rejected because Tabby's team was unable to specify the specific time of the measurements. If a new proposal would ask to take measurements now, and again in six months for comparison, that might be specific enough to be accepted.

Considering we're probably in for the long haul, does anyone know if there's a limit on how long the two observatories can take measurements with the available funding? Or was the funding required for Tabby's team and not for time on these two telescopes?

Their Kickstarter funding for their observation campaign lasts for a year. Hopefully now the star has started acting up again they shouldn't have too much trouble raising more money from another Kickstarter.
Title: Re: Boyajians Star Updates And Discussion
Post by: Mongo62 on 07/24/2017 08:50 PM
Especially since on the 600 day view (two clips up) it's apparent that there are only two cluster of data points, so really statistically all we have is that the flux today, if you low-pass the shorter "weekish" events, is lower than it was some 300 days ago.

There is no reason to think that this is part of downward trend, and doubly no reason to think that this is part of an accelerating downward trend.

Well, there IS the long-term gradual dimming on the order of 20%, between ~1900 and ~1970, recorded on photographic survey plates. And the measured secular dimming (1 or 2 percent?) over the full run of Kepler photometry.

Not that I am endorsing the theory propounded in the videos, that seems far too early to be justified in my opinion. But secular dimming does seem to be happening on a yearly to decadal time scale, the question is how quickly.
Title: Re: Boyajians Star Updates And Discussion
Post by: meekGee on 07/24/2017 08:55 PM
Could be, and clearly something is abnormal here, but if you were to extrapolate the theorized accelerating trend he goes on about to a 70 year extent, where would the star be?
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/24/2017 09:44 PM
Quote
Hi everyone,
 
Here is the latest data for our star. The two new points on the far right (taken in the past 24 hours) are a bit scattered compared to the trend of the past few weeks.  Even so, they remain consistent with the 0.5% depression.
 
First day in a while back in the office for me.  Expect a longer post soon. 
 
~Tabby and team

http://www.wherestheflux.com/single-post/2017/07/24/Dip-update-39n

Also this from her Twitter feed.

Quote
Glen Hunt @RadioGlen
·
What's going on out there?

Tabetha Boyajian @tsboyajian

Replying to @RadioGlen
dunno! whatever it is, its BIG..
8:28 pm · 24 Jul 2017

https://mobile.twitter.com/tsboyajian/status/889567987073773569

Would a dust cloud be so consistent in the amount it blocked over such an extended period. I know there are error bars in the measurements but that seems a very consistent amount to block.
Title: Re: Boyajians Star Updates And Discussion
Post by: M.E.T. on 07/25/2017 06:53 AM
Quote
Hi everyone,
 
Here is the latest data for our star. The two new points on the far right (taken in the past 24 hours) are a bit scattered compared to the trend of the past few weeks.  Even so, they remain consistent with the 0.5% depression.
 
First day in a while back in the office for me.  Expect a longer post soon. 
 
~Tabby and team

http://www.wherestheflux.com/single-post/2017/07/24/Dip-update-39n

Also this from her Twitter feed.

Quote
Glen Hunt @RadioGlen
·
What's going on out there?

Tabetha Boyajian @tsboyajian

Replying to @RadioGlen
dunno! whatever it is, its BIG..
8:28 pm · 24 Jul 2017

https://mobile.twitter.com/tsboyajian/status/889567987073773569

Would a dust cloud be so consistent in the amount it blocked over such an extended period. I know there are error bars in the measurements but that seems a very consistent amount to block.

So my brain is trying to figure out what type of shape would have a profile that fits this depression. So it would seem to me that a relatively small depression, that lasts a long time, means something that does not block a lot of the star's light, but which stays in our field of vision for a long period of time. Meaning either something in a distant orbit which takes a long time to complete its transit, or else something long and thin which lies closer to the star and, although it is therefore transiting much faster, has a length of several millions of miles, thus blocking out the light of the star in a continuous thin line.

Something resembling a long, thin, ring-like swarm, for example. Or I guess something like a massively long, yet relatively thin disk of dust. Is this reasoning in any way valid?
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/25/2017 07:22 AM
Quote
Hi everyone,
 
Here is the latest data for our star. The two new points on the far right (taken in the past 24 hours) are a bit scattered compared to the trend of the past few weeks.  Even so, they remain consistent with the 0.5% depression.
 
First day in a while back in the office for me.  Expect a longer post soon. 
 
~Tabby and team

http://www.wherestheflux.com/single-post/2017/07/24/Dip-update-39n

Also this from her Twitter feed.

Quote
Glen Hunt @RadioGlen
·
What's going on out there?

Tabetha Boyajian @tsboyajian

Replying to @RadioGlen
dunno! whatever it is, its BIG..
8:28 pm · 24 Jul 2017

https://mobile.twitter.com/tsboyajian/status/889567987073773569

Would a dust cloud be so consistent in the amount it blocked over such an extended period. I know there are error bars in the measurements but that seems a very consistent amount to block.

So my brain is trying to figure out what type of shape would have a profile that fits this depression. So it would seem to me that a relatively small depression, that lasts a long time, means something that does not block a lot of the star's light, but which stays in our field of vision for a long period of time. Meaning either something in a distant orbit which takes a long time to complete its transit, or else something long and thin which lies closer to the star and, although it is therefore transiting much faster, has a length of several millions of miles, thus blocking out the light of the star in a continuous thin line.

Something resembling a long, thin, ring-like swarm, for example. Or I guess something like a massively long, yet relatively thin disk of dust. Is this reasoning in any way valid?
Well when you say small we are still talking about something half the size of Jupiter, if not a little larger considering the relative size of the star.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 07/25/2017 07:33 AM
I think the dust model implies that:
- there's a disc of dusty material around the star (say from 1AU to 3AU from the star, if you think the pseudo-periodicity is real; or much further out if you think the secular decline is caused  by dust)
- the disc is essentially edge-on to us
- the dust is unevenly distributed around the orbit.

You don't need *that* much material to explain the dimming because of the large optical depth of dust in our line of sight.  The thing that is hard to explain in this sort of model is the uneven distribution ... so I think there needs to be a (non-transiting) object that provides long-term stability.  [ Either that or we've got lucky and seen a transient event. ]

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/25/2017 07:46 AM
I think the dust model implies that:
- there's a disc of dusty material around the star (say from 1AU to 3AU from the star, if you think the pseudo-periodicity is real; or much further out if you think the secular decline is caused  by dust)
- the disc is essentially edge-on to us
- the dust is unevenly distributed around the orbit.

You don't need *that* much material to explain the dimming because of the large optical depth of dust in our line of sight.  The thing that is hard to explain in this sort of model is the uneven distribution ... so I think there needs to be a (non-transiting) object that provides long-term stability.  [ Either that or we've got lucky and seen a transient event. ]

--- Tony

We shouldn't be limiting ourselves to the dust theory at this stage, especially in the absence of further spectrography data as this seems like an example of putting the cart in front of the horse.

As you can see here Professor Boyajian doesn't commit herself to any solution at this stage.

Quote
Glen Hunt @RadioGlen
Any overall thoughts though? It is bonkers.

Tabetha Boyajian @tsboyajian

Replying to @RadioGlen
Still a crap-shoot

https://mobile.twitter.com/tsboyajian/status/889655890835623936

And more here.

Quote
Anders @AndyHee
I was wondering, are you measuring any wobbles indicating big gravitational effects on the star?

Tabetha Boyajian @tsboyajian

Replying to @AndyHee
Yes we have spectral observations

https://mobile.twitter.com/tsboyajian/status/889655668130623488
Title: Re: Boyajians Star Updates And Discussion
Post by: moreno7798 on 07/26/2017 07:53 PM
I think the dust model implies that:
- there's a disc of dusty material around the star (say from 1AU to 3AU from the star, if you think the pseudo-periodicity is real; or much further out if you think the secular decline is caused  by dust)
- the disc is essentially edge-on to us
- the dust is unevenly distributed around the orbit.

You don't need *that* much material to explain the dimming because of the large optical depth of dust in our line of sight.  The thing that is hard to explain in this sort of model is the uneven distribution ... so I think there needs to be a (non-transiting) object that provides long-term stability.  [ Either that or we've got lucky and seen a transient event. ]

--- Tony

Don't know. The dust model seems to have a problem with the centuries long dimming. and we don't really know if the dimming started a century ago or millennia ago. More data and observation time is needed.

Perhaps a closer to home study is warranted to model the dust behavior in the light curve. Jupiter, Saturn, Uranus, and Neptune . . . but of course we'd have to have the ring edge on.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/26/2017 09:21 PM
Kickstarter update via Reddit.

Quote
Kickstarter update from Tabby.

Not much new photometrically.

Spitzer (near infrared) observations next month, and other observations planned for later this year and March of next year. Hopefully during a dip, but of course we don't know.

Money for LCO runs out on November 30th, possibly more crowdfunding needed. That is about when it starts to get tough to see the star at good photometric elevations from LCO.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/27/2017 07:13 AM
Can Dips of Boyajian’s Star be Explained by Circumsolar Rings?

Quote
Abstract

Could the dips of “Boyajian’s Star” (KIC 8462852) have been caused by matter in our Solar System? The interval between periods of deep dips is nearly twice the orbital period of the Kepler satellite. I consider heliocentric obscuring rings in the outer Solar System that graze the line of sight to the star once per Kepler orbit. The hypothesis predicts that future dips may be observed from Earth during windows separated by a year, although their detailed structure depends on the distribution of particles along the ring. Dips observed at terrestrial sites separated by >1000 km in a direction perpendicular to the Earth’s orbital motion may be uncorrelated.

https://academic.oup.com/mnras/article-abstract/doi/10.1093/mnras/stx1876/4036879/Can-Dips-of-Boyajian-s-Star-be-Explained-by
Title: Re: Boyajians Star Updates And Discussion
Post by: notsorandom on 07/27/2017 02:20 PM
Can Dips of Boyajian’s Star be Explained by Circumsolar Rings?

Quote
Abstract

Could the dips of “Boyajian’s Star” (KIC 8462852) have been caused by matter in our Solar System? The interval between periods of deep dips is nearly twice the orbital period of the Kepler satellite. I consider heliocentric obscuring rings in the outer Solar System that graze the line of sight to the star once per Kepler orbit. The hypothesis predicts that future dips may be observed from Earth during windows separated by a year, although their detailed structure depends on the distribution of particles along the ring. Dips observed at terrestrial sites separated by >1000 km in a direction perpendicular to the Earth’s orbital motion may be uncorrelated.

https://academic.oup.com/mnras/article-abstract/doi/10.1093/mnras/stx1876/4036879/Can-Dips-of-Boyajian-s-Star-be-Explained-by
Why didn't Kepler see any other stars in its field of view near this one dim in the same way?
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 07/27/2017 04:47 PM
Can Dips of Boyajian’s Star be Explained by Circumsolar Rings?

Quote
Abstract

Could the dips of “Boyajian’s Star” (KIC 8462852) have been caused by matter in our Solar System? The interval between periods of deep dips is nearly twice the orbital period of the Kepler satellite. I consider heliocentric obscuring rings in the outer Solar System that graze the line of sight to the star once per Kepler orbit. The hypothesis predicts that future dips may be observed from Earth during windows separated by a year, although their detailed structure depends on the distribution of particles along the ring. Dips observed at terrestrial sites separated by >1000 km in a direction perpendicular to the Earth’s orbital motion may be uncorrelated.

https://academic.oup.com/mnras/article-abstract/doi/10.1093/mnras/stx1876/4036879/Can-Dips-of-Boyajian-s-Star-be-Explained-by
Why didn't Kepler see any other stars in its field of view near this one dim in the same way?
How would this theory reconcile the need for an object within our solar system to have its own proper motion against the stelar background as it orbits our sun?  considering Tabby's star is quite far from the ecliptic, the proposed objects motion should be moving it away from an annual occultation at a pretty high angular rate.   The object would have to be huge to still be occulting Tabby's star at each annual alignment of Kepler.  Not buying this this theory without lots more explaining.
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 07/27/2017 05:01 PM
Why didn't Kepler see any other stars in its field of view near this one dim in the same way?
Remember, Kepler only returns "postage stamps" for selected stars (except for very occasional full frame images), so there's a bit more wiggle room than you might expect.

Here's a pre-print of the paper https://arxiv.org/abs/1705.08377

Wright considered this kind of theory (though a "cloud" rather than a heliocentric ring) in his review http://sites.psu.edu/astrowright/2016/08/31/what-could-be-going-on-with-boyajians-star-part-iv-nearby-stars-instrumental-effects-and-a-solar-system-cloud/
He rated it as "unclear"
Quote
Nonetheless, the combination of a highly speculative cloud, a missing annual timescale, no obvious dimming of neighbor stars, and no clear sodium absorption feature cause me to give a subjective rating of unclear to this one.  That is, I’ll need some outer Solar System people to weigh in on likelihoods before I give it a grade.

Also, this may have been tested with last set of dips:
Quote
Dips observed at terrestrial sites separated by > 1000 km in a direction perpendicular to the Earth's orbital motion may be uncorrelated.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/27/2017 06:57 PM
Hefty update.

Quote
July 27, 2017
[Orig: July, 26 2017]
 
Hi everyone,
 
To update you on recent developments:
Below is the latest light curve.  As you can see, nothing drastic has happened, but the star still doesnt appear quite back to its "normal" state.

Quote
We have been working on the quality of the pipeline. Here is another plot to show slight changes made to the light curve, in particular after day~50.  This is because we now include a new adjustment to the data, or "detrending", to correct for unwanted systematic trends that were introduced when we adjusted the telescope pointing at that time. The blue "OGG-detrended" points here are the ones that have been corrected, and this is what is used in the light curve above.

Quote
Our new LCO contract to increase our number of hours on the network this semester is signed. We now have ~200 hours remaining on the 40cm network for the 2017 AB semester, which ends November 30, 2017. This will allow us to continue our current observing sequence at a comfortable cadence.  I am still chewing on the idea for another crowd funding effort, and I appreciate the words of support and advice have given me so far.
In other news, our colleague Huan Meng (PI of the Spitzer monitoring program for this star) informed us earlier this week that the next observation is scheduled for August 16, UTC 12:20:02 (typical time uncertainty ~10 min or less).  That's about 2 days after the star becomes observable by Spitzer. (We will coordinate observations with Swift to be taken at the same time, and of course LCO will also have its eyes on it!) After this, the next Spitzer observation will come between November 16 and December 15, and the one after will be at some point between March 1 and March 23 next year. If the star starts to act up again, we may submit a DD proposal at any time to increase this frequency.
 
All the best, 
         
~Tabby and team

http://www.wherestheflux.com/single-post/2017/07/27/Dip-update-39n
Title: Re: Boyajians Star Updates And Discussion
Post by: KelvinZero on 07/28/2017 01:24 AM
Can Dips of Boyajian’s Star be Explained by Circumsolar Rings?
Maybe we have just spotted the seam between the panels in the massive planetarium we have been living in all this time  ;)
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/28/2017 07:17 AM
Can Dips of Boyajian’s Star be Explained by Circumsolar Rings?
Maybe we have just spotted the seam between the panels in the massive planetarium we have been living in all this time  ;)

Here's the non-paywall version of that paper.

Quote
Can Dips of Boyajian's Star be Explained by Circumsolar Rings?

Could the dips of "Boyajian's Star" (KIC 8462852) have been caused by matter in our Solar System? The interval between periods of deep dips is nearly twice the orbital period of the Kepler satellite. I consider heliocentric obscuring rings in the outer Solar System that graze the line of sight to the star once per orbit of Kepler. The hypothesis predicts that future dips may be observed from Earth during windows separated by a year, although their detailed structure depends on the distribution of particles along the ring. Dips observed at terrestrial sites separated by > 1000 km in a direction perpendicular to the Earth's orbital motion may be uncorrelated.
Comments:6 pages, 4 figures; revised and expanded

https://arxiv.org/abs/1705.08377
Title: Re: Boyajians Star Updates And Discussion
Post by: high road on 07/28/2017 09:07 AM
Hefty update.

Quote
July 27, 2017
[Orig: July, 26 2017]
 
Hi everyone,
 
To update you on recent developments:
Below is the latest light curve.  As you can see, nothing drastic has happened, but the star still doesnt appear quite back to its "normal" state.

Quote
We have been working on the quality of the pipeline. Here is another plot to show slight changes made to the light curve, in particular after day~50.  This is because we now include a new adjustment to the data, or "detrending", to correct for unwanted systematic trends that were introduced when we adjusted the telescope pointing at that time. The blue "OGG-detrended" points here are the ones that have been corrected, and this is what is used in the light curve above.

Quote
Our new LCO contract to increase our number of hours on the network this semester is signed. We now have ~200 hours remaining on the 40cm network for the 2017 AB semester, which ends November 30, 2017. This will allow us to continue our current observing sequence at a comfortable cadence.  I am still chewing on the idea for another crowd funding effort, and I appreciate the words of support and advice have given me so far.
In other news, our colleague Huan Meng (PI of the Spitzer monitoring program for this star) informed us earlier this week that the next observation is scheduled for August 16, UTC 12:20:02 (typical time uncertainty ~10 min or less).  That's about 2 days after the star becomes observable by Spitzer. (We will coordinate observations with Swift to be taken at the same time, and of course LCO will also have its eyes on it!) After this, the next Spitzer observation will come between November 16 and December 15, and the one after will be at some point between March 1 and March 23 next year. If the star starts to act up again, we may submit a DD proposal at any time to increase this frequency.
 
All the best, 
         
~Tabby and team

http://www.wherestheflux.com/single-post/2017/07/27/Dip-update-39n

Strange. There seems to be a difference between the TFN observations in update 40 and 41.

Edit: More specifically, the clearest difference is that the string of consistent values of last week (update 38) seems to have disappeared between update 40 and 41. Over all, the apparent 'downward slope' of the last few weeks vanishes and is replaced by fluctuations toward normal. Have the TFN observations been recalibrated as well?
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/28/2017 09:10 AM
Hefty update.

Quote
July 27, 2017
[Orig: July, 26 2017]
 
Hi everyone,
 
To update you on recent developments:
Below is the latest light curve.  As you can see, nothing drastic has happened, but the star still doesnt appear quite back to its "normal" state.

Quote
We have been working on the quality of the pipeline. Here is another plot to show slight changes made to the light curve, in particular after day~50.  This is because we now include a new adjustment to the data, or "detrending", to correct for unwanted systematic trends that were introduced when we adjusted the telescope pointing at that time. The blue "OGG-detrended" points here are the ones that have been corrected, and this is what is used in the light curve above.

Quote
Our new LCO contract to increase our number of hours on the network this semester is signed. We now have ~200 hours remaining on the 40cm network for the 2017 AB semester, which ends November 30, 2017. This will allow us to continue our current observing sequence at a comfortable cadence.  I am still chewing on the idea for another crowd funding effort, and I appreciate the words of support and advice have given me so far.
In other news, our colleague Huan Meng (PI of the Spitzer monitoring program for this star) informed us earlier this week that the next observation is scheduled for August 16, UTC 12:20:02 (typical time uncertainty ~10 min or less).  That's about 2 days after the star becomes observable by Spitzer. (We will coordinate observations with Swift to be taken at the same time, and of course LCO will also have its eyes on it!) After this, the next Spitzer observation will come between November 16 and December 15, and the one after will be at some point between March 1 and March 23 next year. If the star starts to act up again, we may submit a DD proposal at any time to increase this frequency.
 
All the best, 
         
~Tabby and team

http://www.wherestheflux.com/single-post/2017/07/27/Dip-update-39n

Strange. There seems to be a difference between the TFN observations in update 40 and 41.


Here is 41/n.

http://www.wherestheflux.com/single-post/2017/07/27/Dip-update-41n
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/28/2017 04:06 PM
Another update.

Quote
Dip update 42/n
July 28, 2017
[Orig: July, 28 2017]
 
Hi everyone,
 
The latest update from LCO.  Weather has made scheduling at both stations (OGG and TFN) difficult, limiting the time observing to about an hour at each location. Still, our results remain consistent with a reduced flux state compared to pre and post Elsie levels.  Note that the detrending of the data mentioned in a recent post (40/n) is now also applied to the TFN data as well as OGG.  This detrending basically only effects the data taken after day ~50 (MJD 57930) when we made changes to our observing configuration.
 
The correction is also pretty small, most of the time within the measurement errors on the uncorrected points.  Applying this same technique to the comparison star light curves showed clear improvement, indicating the detrending correction, while small, is necessary.             
 
All the best, 
         
~Tabby and team

http://www.wherestheflux.com/single-post/2017/07/28/Dip-update-42n
Title: Re: Boyajians Star Updates And Discussion
Post by: high road on 07/28/2017 04:21 PM
Detrending seems to have quite a significant effect. Doesn't look like the accelerated dimming anymore, no matter what points you ignore.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/28/2017 05:51 PM
Detrending seems to have quite a significant effect. Doesn't look like the accelerated dimming anymore, no matter what points you ignore.

Bit early to be declaring that I would have thought.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/28/2017 07:52 PM
https://www.youtube.com/watch?v=WvozpihAeeA
Title: Re: Boyajians Star Updates And Discussion
Post by: meekGee on 07/29/2017 04:43 AM
Detrending seems to have quite a significant effect. Doesn't look like the accelerated dimming anymore, no matter what points you ignore.
IMO the data never pointed to accelerating dimming.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/29/2017 08:11 AM
A lot of lay people such as myself have been confused by the adjustment of the data especially as the reasons given have been overly technical and incomplete in my opinion. Even those I've seen online who obviously know more about the technicalities have been left only able to talk in generalities due to the lack of specifics given. It has also led to others losing faith in the data being given, again due to lack of proper explanation.
Title: Re: Boyajians Star Updates And Discussion
Post by: high road on 07/29/2017 09:10 AM
Detrending seems to have quite a significant effect. Doesn't look like the accelerated dimming anymore, no matter what points you ignore.
IMO the data never pointed to accelerating dimming.

Let me rephrase that: the apparent dimming trend since the second dip has all but disappeared now. Regardless of how long it would have lasted.

Not exactly surprised by the reaction. Even though it's only a small change to each data point, the overall effect is quite significant.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/29/2017 08:22 PM
To expand on my comments above. Does what she said mean the neighbouring stars also had this bogus dimming? "Detrending" which is the specific term she used suggests a trend was removed. That's different to an offset adjustment. That part needs to be explained?
Title: Re: Boyajians Star Updates And Discussion
Post by: meekGee on 07/29/2017 10:16 PM
From here:  https://xkcd.com/605/
Title: Re: Boyajians Star Updates And Discussion
Post by: Mongo62 on 07/29/2017 10:56 PM
https://www.youtube.com/watch?v=NuFN8M-Z8kM

Fredric Parker is looking at AASVO observations for an independent dataset. I admit that had been my first thought as well, but when I looked at their website, it appeared that their measurements had far too much scatter to be useful. However, some individual AASVO observers appear to produce surprisingly stable and consistent results, including the observer whose results are presented in the above video.

This observer's visual brightness trend for this star follows the 0.4% per month decrease that had earlier been presented on Fredric Parker's videos.  I checked the actual Kepler paper -- the first 3 years of data showed a steady 0.025% per month decline, which then accelerated to a 0.21% per month decline for the next seven months, before returning to its earlier rate of decline. So the star shows at least two rates of brightness decline -- a slower rate of 0.3% per year, and a faster rate of 2.5% per year.

I personally am skeptical that the star's brightness decline -- while real -- is as quick as Fredric Parker suggests. Looking at his plots of brightness versus time, I think that it could just as easily show a steady decline over the time plotted, of about the same slope as the quicker Kepler-observed decline.

This does however cast doubt on Tabby's "detrending", which was applied without any actual explanation or justification given. I would want to see the raw data for both Boyajian's Star and any nearby comparison stars, to see any trends in the measured differences in observed brightness between them.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/29/2017 11:43 PM
https://www.youtube.com/watch?v=NuFN8M-Z8kM

Fredric Parker is looking at AASVO observations for an independent dataset. I admit that had been my first thought as well, but when I looked at their website, it appeared that their measurements had far too much scatter to be useful. However, some individual AASVO observers appear to produce surprisingly stable and consistent results, including the observer whose results are presented in the above video.

This observer's visual brightness trend for this star follows the 0.4% per month decrease that had earlier been presented on Fredric Parker's videos.  I checked the actual Kepler paper -- the first 3 years of data showed a steady 0.025% per month decline, which then accelerated to a 0.21% per month decline for the next seven months, before returning to its earlier rate of decline. So the star shows at least two rates of brightness decline -- a slower rate of 0.3% per year, and a faster rate of 2.5% per year.

I personally am skeptical that the star's brightness decline -- while real -- is as quick as Fredric Parker suggests. Looking at his plots of brightness versus time, I think that it could just as easily show a steady decline over the time plotted, of about the slope of the quicker Kepler-observed decline.

This does however cast doubt on Tabby's "detrending", which was applied without any actual explanation or justification given. I would want to see the raw data for both Boyajian's Star and any nearly comparison stars, to see any trends in the measured differences in observed brightness between them.
That's what I've been saying there was no proper explanation given for the detrending. Which is what has made some annoyed. It seems clear that Fredric Parker is no longer going to use the data produced by her team.
Title: Re: Boyajians Star Updates And Discussion
Post by: moreno7798 on 07/30/2017 02:22 AM
From here:  https://xkcd.com/605/

Except that "a century's worth of recorded information suggests that the bride has gradually been marrying from 1890 to 1989 by about 20 husbands a year.

Oh well, I'm guessing that bride will indeed have more than four dozen husbands! . . . .

Let's extrapolate even further . . . I'm guessing you just chose to forget that little fact.
Title: Re: Boyajians Star Updates And Discussion
Post by: meekGee on 07/30/2017 02:32 AM
From here:  https://xkcd.com/605/

Except that "a century's worth of recorded information suggests that the bride has gradually been marrying men from 1890 to 1989 by about 20 men a year.

Oh well, I'm guessing you just chose to forget that little fact.
The bride graph is a generic, tongue in cheek commentary about extrapolation.

The claim in the vid clips about ACCELERATED dimming was made basically based on two very narrow data clusters.   Definitely bride syndrome​.

The longer term (~century) dimming can't possibly be judged as "accelerating", since such acceleration, if detectable, would have integrated itself into zeron brightness by now.

So what remains is that possibly, between today and 100 years ago, the star appears to have dimmed.

Also, in recent times, it's observed to be all over the place.

Those are fine claims.

However, if the appears to be "oddly variable", the observations from 100 years ago - are there enough of them to establish a "nominal level", or did we just catch it, 100 years ago, at a momentary bright day?
Title: Re: Boyajians Star Updates And Discussion
Post by: moreno7798 on 07/30/2017 03:04 AM
From here:  https://xkcd.com/605/

Except that "a century's worth of recorded information suggests that the bride has gradually been marrying men from 1890 to 1989 by about 20 men a year.

Oh well, I'm guessing you just chose to forget that little fact.
The bride graph is a generic, tongue in cheek commentary about extrapolation.

The claim in the vid clips about ACCELERATED dimming was made basically based on two very narrow data clusters.   Definitely bride syndrome​.

The longer term (~century) dimming can't possibly be judged as "accelerating", since such acceleration, if detectable, would have integrated itself into zeron brightness by now.

So what remains is that possibly, between today and 100 years ago, the star appears to have dimmed.

Also, in recent times, it's observed to be all over the place.

Those are fine claims.

However, if the appears to be "oddly variable", the observations from 100 years ago - are there enough of them to establish a "nominal level", or did we just catch it, 100 years ago, at a momentary bright day?

Well, you establish nominal levels from other F-type main-sequence stars - If the vast majority of other F-type main-sequence stars follow a trend in brightness then it's a safe bet that his one was at one point pretty much the same.

The accelerating dimming observation was made based on data. As far as I'm concerned the interpretation of the data was correct. I don't think it was premature to extrapolate either as - once again - the interpretation was correct. So there's nothing wrong with making an observation based on data. Now, if the data being provided was erroneous, then that's not an error from the interpreter, that's an error coming from those obtaining the data. Let's put the blame where it belongs.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/30/2017 06:39 AM
Quote
Dip update 43/n

July 29, 2017

[Orig: July, 29 2017]

 

Hi everyone,

 

The latest update from LCO.  Only data TFN to report, the weather was bad at OGG.

 

Have a great weekend, 

         

~Tabby and team

http://www.wherestheflux.com/single-post/2017/07/29/Dip-update-43n
Title: Re: Boyajians Star Updates And Discussion
Post by: high road on 07/30/2017 08:35 AM
Here's some more extrapolation. Which is completely fine as everyone is aware of it being only a thought experiment to see if future observations match the prediction.

The observations in Tabby's team's detrended data seem to be moving apart. The last ten or so red data points are consistently below the blue ones. If this remains, and the observatories focus on slightly different wavelengths, that tells us something about how the star is dimming, other than endlessly debating how much data is enough to be able to extrapolate over the next few decades. Could be why they decided to detrend. Especially because detrending is all about removing the downward trend.

This means we need to read the new graph differently. If new measurements are conistently below the horizontal line, the dimming is accellerating. If they are above, the dimming is slowing down or reversing. Basically, a different way to show the same thing as Fredrics team. Ideally, Tabby should continually show us both the raw data and the detrended data, but I understand her reluctance to give out too many gifts to other researchers who might beat her to the punch in writing papers about it. Only providing processed data without saying how they were processed prevents that.

Edit: sorry for autocorrect and other typo's. Typing this on new phone.

Edit 2: so based on the new graph, if the trend has been correctly removed, the dimming has been accellerating. While recently, the accelleration seems to be slowing down in the blue data points, but not in the red.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/30/2017 09:08 AM
I do like the fact that rather than just complaining about the data provided, Fredric Parker is going about setting up his own independent source of data. Just a shame he keeps wanting to fit his own personal theory on top of it all the time.
Title: Re: Boyajians Star Updates And Discussion
Post by: LouScheffer on 07/30/2017 09:01 PM
In Boyajian's post  (http://www.wherestheflux.com/single-post/2017/07/27/Dip-update-39n)she says:
Quote
Here is another plot to show slight changes made to the light curve, in particular after day~50.  This is because we now include a new adjustment to the data, or "detrending", to correct for unwanted systematic trends that were introduced when we adjusted the telescope pointing at that time. The blue "OGG-detrended" points here are the ones that have been corrected, and this is what is used in the light curve above.

and  also (http://www.wherestheflux.com/single-post/2017/07/28/Dip-update-42n)
Quote
Note that the detrending of the data mentioned in a recent post (40/n) is now also applied to the TFN data as well as OGG.  This detrending basically only effects the data taken after day ~50 (MJD 57930) when we made changes to our observing configuration.
 
The correction is also pretty small, most of the time within the measurement errors on the uncorrected points.  Applying this same technique to the comparison star light curves showed clear improvement, indicating the detrending correction, while small, is necessary.

And on June 26, she said (http://)
Quote
Note: on June 26 (~45 on the x-axis) and after, there have been two 40cm telescopes at each of the LCO stations (OGG and TFN) taking observations of our star (instead of one at each station)...
So on day 45, they changed from one telescope per site to two.  On day 50, they changed the telescope pointing. (If I had to guess, I'd say put the star off center in a different way in the two scopes.  Then they could get more comparison stars.).   When they did this, they started to see changes, starting at that time, in the comparison stars in the same field of view.  Since the ensemble of comparison stars is believed to be stable, they assume this is an instrumental effect, and calculated a detrending that results in more constant comparison stars.  They then apply this to the unknown Boyajian's star.

This seems sensible to me.   The only problem is that some theories (like interstellar clouds) could cause neighboring stars to vary, too, and you don't want to throw that out.   But if it improves almost all of the comparison stars, of differing separation from Boyajian's star, then it's probably a sensible correction.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/30/2017 10:36 PM
It really boils down to needing more clarity on the adjustments.
Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 07/30/2017 11:00 PM
It really boils down to needing more clarity on the adjustments.
I would assume the data published by Boyajian's group is intended to give supporters and interested community a general idea what is going on: i.e. is the star currently dipping or doing something else that would justify additional observation. It isn't meant to be publication quality data, and it would be unreasonable to expect them to make that kind of data public before they publish. They are being pretty open by professional astronomy standards.

Any long term observation like this will need careful analysis and correction for instrumental effects, and that effort is likely to be ongoing.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/31/2017 06:01 AM
It really boils down to needing more clarity on the adjustments.
I would assume the data published by Boyajian's group is intended to give supporters and interested community a general idea what is going on: i.e. is the star currently dipping or doing something else that would justify additional observation. It isn't meant to be publication quality data, and it would be unreasonable to expect them to make that kind of data public before they publish. They are being pretty open by professional astronomy standards.

Any long term observation like this will need careful analysis and correction for instrumental effects, and that effort is likely to be ongoing.
That's a fair point. But also adjusting the data without fully explaining why you've had to adjust it has led to an erosion in trust in it from some quarters.
Title: Re: Boyajians Star Updates And Discussion
Post by: high road on 07/31/2017 08:36 AM

Tabby's latest update:

Quote
Hi everyone,
 

The latest update from LCO. 


It looks like we could have caught some short-term variability over the past 36 hours: the latest blue point from TFN was significantly lower than the pervious day, and by the time OGG observed the star its brightness was back to normal.
 

Best,     
         

~Tabby and team 

http://www.wherestheflux.com/single-post/2017/07/30/Dip-update-44n (http://www.wherestheflux.com/single-post/2017/07/30/Dip-update-44n)

Visual comparison between this graph and the previous one shows that some older data points continue to shift upwards. I assume this is due to the detrending that is being applied. However, I don't really understand how that would work if the detrending is relative to the reference stars (where I presume the variation in the reference stars is deducted from the variation in this star), rather than to the evolution in the star itself (where each new measurement shifts the trend somewhat and older data would be recalculated relative to that new trend).
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/31/2017 09:24 AM
Bruce Gary appears to be back in operation.

Via Reddit.

Quote
Mag V: 31 July = 11.9131 +/- .0017 compared to 2 May = 11.9068 +/- .0020

That is around 0.58% (+/- 0.3%) down on early May.
Title: Re: Boyajians Star Updates And Discussion
Post by: Mongo62 on 07/31/2017 03:38 PM
Bruce Gary appears to be back in operation.

Via Reddit.

Quote
Mag V: 31 July = 11.9131 +/- .0017 compared to 2 May = 11.9068 +/- .0020

That is around 0.58% (+/- 0.3%) down on early May.

I immediately compared the differences to the Boyajian measurements, both pre-detrending and post-detrending.

If the Bruce Gary measurement was at the same time as the TFN measurement, then it matches the post-detrended numbers. But if it was at the same time as the OGG measurement, then it matches the pre-detrended numbers.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/31/2017 04:03 PM
Here is the latest update 45/n.

http://www.wherestheflux.com/single-post/2017/07/31/Dip-update-45n
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 07/31/2017 08:11 PM
Recent talk by Jason Wright.

https://www.youtube.com/watch?v=ZZDTz7j_NNQ
Title: Re: Boyajians Star Updates And Discussion
Post by: Orbiter on 08/01/2017 12:37 PM
Email sent out by Bruce Gary:

Quote
All, I had an hour of clear skies last night, plus some thin cirrus time, which was enough to obtain a usable V-mag for KIC846. I think the inescapable conclusions are that: 1) V-mag is now 1 % fainter than in late 2016, 2) whereas much of this summer included fade events the times of no fade exhibit a continuation of a long-term fading that appears to be accelerating and 3) my V-mag measurements are compatible with the Tabby Team V-mags in showing a very slow pace for recovery from the two main fade events of May and June. It is important for me to acquire more observations with clear skies in order to be sure of associating the present levels with the non-fade state. If later this week, when I expect a clearing for a couple nights, I measure the same V-mags as last night, then I will be convinced that we're now in a recovered state and will begin to think about refining my long-term fade model in a way that produces a more "accelerated" fade (i.e., an inverted Gaussian with a shorter timescale and possibly deeper depth). I'm sure Fred Parker will be happy to see that happen since he was the first person to emphasize this aspect of my data:-) The 3rd graph below is a first attempt to refine the long-term fade model for use with the 2017 data (just a linear model). The last graph is my current inverted-Gaussian model, that is poised for revision. Bruce

Amazing. If it's shown that the star doesn't ever fully recover to its brightness from before the May and June dimming events, then that might just rule out anything orbiting the star being the culprit.
Title: Re: Boyajians Star Updates And Discussion
Post by: sghill on 08/01/2017 01:12 PM
Email sent out by Bruce Gary:

Quote
All, I had an hour of clear skies last night, plus some thin cirrus time, which was enough to obtain a usable V-mag for KIC846. I think the inescapable conclusions are that: 1) V-mag is now 1 % fainter than in late 2016, 2) whereas much of this summer included fade events the times of no fade exhibit a continuation of a long-term fading that appears to be accelerating and 3) my V-mag measurements are compatible with the Tabby Team V-mags in showing a very slow pace for recovery from the two main fade events of May and June. It is important for me to acquire more observations with clear skies in order to be sure of associating the present levels with the non-fade state. If later this week, when I expect a clearing for a couple nights, I measure the same V-mags as last night, then I will be convinced that we're now in a recovered state and will begin to think about refining my long-term fade model in a way that produces a more "accelerated" fade (i.e., an inverted Gaussian with a shorter timescale and possibly deeper depth). I'm sure Fred Parker will be happy to see that happen since he was the first person to emphasize this aspect of my data:-) The 3rd graph below is a first attempt to refine the long-term fade model for use with the 2017 data (just a linear model). The last graph is my current inverted-Gaussian model, that is poised for revision. Bruce

Amazing. If it's shown that the star doesn't ever fully recover to its brightness from before the May and June dimming events, then that might just rule out anything orbiting the star being the culprit.

Perhaps the dips are corresponding to convection within the star. It may have some weird rapid convection cycle that lowers the pressure near the core, and correspondly reduces the fusion occurring there. We'd notice it when the light emerges as a dip in the solar light output.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/01/2017 01:16 PM
Email sent out by Bruce Gary:

Quote
All, I had an hour of clear skies last night, plus some thin cirrus time, which was enough to obtain a usable V-mag for KIC846. I think the inescapable conclusions are that: 1) V-mag is now 1 % fainter than in late 2016, 2) whereas much of this summer included fade events the times of no fade exhibit a continuation of a long-term fading that appears to be accelerating and 3) my V-mag measurements are compatible with the Tabby Team V-mags in showing a very slow pace for recovery from the two main fade events of May and June. It is important for me to acquire more observations with clear skies in order to be sure of associating the present levels with the non-fade state. If later this week, when I expect a clearing for a couple nights, I measure the same V-mags as last night, then I will be convinced that we're now in a recovered state and will begin to think about refining my long-term fade model in a way that produces a more "accelerated" fade (i.e., an inverted Gaussian with a shorter timescale and possibly deeper depth). I'm sure Fred Parker will be happy to see that happen since he was the first person to emphasize this aspect of my data:-) The 3rd graph below is a first attempt to refine the long-term fade model for use with the 2017 data (just a linear model). The last graph is my current inverted-Gaussian model, that is poised for revision. Bruce

Amazing. If it's shown that the star doesn't ever fully recover to its brightness from before the May and June dimming events, then that might just rule out anything orbiting the star being the culprit.

Your statement is seemingly negated by this recent update by Bruce Gary in which he clear states that it is belief that the dips are caused by orbiting dust clouds.

Quote
"It's good when two completely different observatories show essentially the same brightness variation. The one difference between HAO and Tabby Team normalized flux in Fig. 1.3 is the depth of the second dip, at x = 47. This can be explained by noting that HAO measurements were made with a V-band filter and the Tabby Team measurements were made with a longer wavelength r'-band filter. If the dust cloud that produced this fade event has a particle size distribution that extends to smaller than ~ 0.5 micron, then such differences in depth can be expected. The fact that this difference is present for the second dip suggests that the second dust cloud did indeed have a component of small particles. Likewise, the lack of depth difference for the first dip (at x = 18) suggests that that dust cloud lacked a component of small particles."
Title: Re: Boyajians Star Updates And Discussion
Post by: high road on 08/01/2017 06:20 PM
Recent talk by Jason Wright.

https://www.youtube.com/watch?v=ZZDTz7j_NNQ

So, there are other stars exhibiting the same behavior as Tabby's star, but with excess IR? Interesting. Does he mean occasionally dropping 20%, dimming for weeks on end or dimming continuously for decades? If all three, how likely is it that Tabby's star is actually going through the same phenomenon, where IR is emitted asymmetrically and it's the only one where the relative position of whatever is blocking the light means the IR is not emitted towards us?

Second interesting thing: the first measurement in Tabby's graph back on the horizontal line coincides with the first day of no clear shift in previous data. Bit early to be more than just interesting, certainly not enough to repeat myself.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/01/2017 07:11 PM
Quote
Jason Wright
Jason Wright @Astro_Wright
All of the @GrnBnkTelescope data from our @BerkeleySETI run on @tsboyajian's star are finally here at @PSUScience! *Whew!*

https://mobile.twitter.com/Astro_Wright/status/892454485754351622
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/01/2017 08:45 PM
Quote
Dip update 46/n
August 1, 2017
[Orig: Aug 1, 2017]
 
Hi everyone,
 
Lots of great data from LCO last night. Looks like a continuing normal brightness level.
 
Best,     
         
~Tabby and team

http://www.wherestheflux.com/single-post/2017/08/01/Dip-update-46n
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 08/01/2017 08:53 PM
Recent talk by Jason Wright.

https://www.youtube.com/watch?v=ZZDTz7j_NNQ

So, there are other stars exhibiting the same behavior as Tabby's star, but with excess IR? Interesting. Does he mean occasionally dropping 20%, dimming for weeks on end or dimming continuously for decades? If all three, how likely is it that Tabby's star is actually going through the same phenomenon, where IR is emitted asymmetrically and it's the only one where the relative position of whatever is blocking the light means the IR is not emitted towards us?

Second interesting thing: the first measurement in Tabby's graph back on the horizontal line coincides with the first day of no clear shift in previous data. Bit early to be more than just interesting, certainly not enough to repeat myself.

Not the same behaviour, though superficially similar.  He is referring to YSOs, young stellar objects, basically stars young enough to still have debris disks and are actively forming planets.  These are unmistakable from their infrared excess. No long term dimming noted though and the dipping has a different quality to it. Probably a good paper to read about it this one; https://arxiv.org/pdf/1608.07291.pdf
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/02/2017 07:25 PM
Possibly the start of a new dip.

http://www.wherestheflux.com/single-post/2017/08/02/Dip-update-47n
Title: Re: Boyajians Star Updates And Discussion
Post by: Mongo62 on 08/03/2017 02:19 AM
Quote
Dip update 46/n
August 1, 2017
[Orig: Aug 1, 2017]
 
Hi everyone,
 
Lots of great data from LCO last night. Looks like a continuing normal brightness level.
 
Best,     
         
~Tabby and team

http://www.wherestheflux.com/single-post/2017/08/01/Dip-update-46n

Big disconnect between this and what Bruce Gary is observing. I am much more inclined to believe Bruce Gary's numbers than Tabby Boyajian's "detrended" numbers, at this time.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/03/2017 05:36 AM
Quote
Dip update 46/n
August 1, 2017
[Orig: Aug 1, 2017]
 
Hi everyone,
 
Lots of great data from LCO last night. Looks like a continuing normal brightness level.
 
Best,     
         
~Tabby and team

http://www.wherestheflux.com/single-post/2017/08/01/Dip-update-46n

Big disconnect between this and what Bruce Gary is observing. I am much more inclined to believe Bruce Gary's numbers than Tabby Boyajian's "detrended" numbers, at this time.

Did you see her 47/n update (as posted above)?
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 08/03/2017 06:19 AM
Quote
Dip update 46/n
August 1, 2017
[Orig: Aug 1, 2017]
 
Hi everyone,
 
Lots of great data from LCO last night. Looks like a continuing normal brightness level.
 
Best,     
         
~Tabby and team

http://www.wherestheflux.com/single-post/2017/08/01/Dip-update-46n

Big disconnect between this and what Bruce Gary is observing. I am much more inclined to believe Bruce Gary's numbers than Tabby Boyajian's "detrended" numbers, at this time.

Well for a start they are taken with different filters.  If the longer-term dimming is due to fine-grained dust you'd expect Bruce's observations to be more sensitive to it.
Title: Re: Boyajians Star Updates And Discussion
Post by: jebbo on 08/03/2017 08:50 AM
Big disconnect between this and what Bruce Gary is observing. I am much more inclined to believe Bruce Gary's numbers than Tabby Boyajian's "detrended" numbers, at this time.

Why? 

--- Tony
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/03/2017 09:04 AM
Big disconnect between this and what Bruce Gary is observing. I am much more inclined to believe Bruce Gary's numbers than Tabby Boyajian's "detrended" numbers, at this time.

Why? 

--- Tony

I imagine the poster is amongst a number of people unhappy with what what they see as the manipulation of the data through the detrending.
Title: Re: Boyajians Star Updates And Discussion
Post by: Alpha_Centauri on 08/03/2017 09:10 AM
Big disconnect between this and what Bruce Gary is observing. I am much more inclined to believe Bruce Gary's numbers than Tabby Boyajian's "detrended" numbers, at this time.

Why? 

--- Tony

I imagine the poster is amongst a number of people unhappy with what what they see as the manipulation of the data through the detrending.

Which doesn't make much sense as Bruce has been doing some heavy detrending himself...
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/03/2017 09:13 AM
Big disconnect between this and what Bruce Gary is observing. I am much more inclined to believe Bruce Gary's numbers than Tabby Boyajian's "detrended" numbers, at this time.

Why? 

--- Tony

I imagine the poster is amongst a number of people unhappy with what what they see as the manipulation of the data through the detrending.

Which doesn't make much sense as Bruce has been doing some heavy detrending himself...

Maybe they feel more that they understand the reasons he did that than the other team, though she gave an explanation people appear to be wanting more clarity on her reasoning for the decision.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/03/2017 08:10 PM
Looks like we are inching into a new dip.

Quote
Dip update 48/n
August 3, 2017
[Orig: Aug 3, 2017]
 
Hi everyone,
 
And again, lots of great data from LCO last night.  We continue to inch our way backwards down the number line (the 'number line' here refers to the brightness, not age/time! #PhishQuotesForScience).   
 
Best,     
         
~Tabby and team

http://www.wherestheflux.com/single-post/2017/08/03/Dip-update-48n
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/04/2017 07:44 AM
Fredric Parker's latest video in which he talks about his engineering background and why he has a differing approach to academia. Also why he has stopped using Professor Boyajian's data. Finally he puts forward Bruce Gary's explanation for the events concerning this star.

https://www.youtube.com/watch?v=ifJ_DhfH96Y
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/05/2017 01:40 AM
You can see the latest Bruce Gary data presented in this video.

https://www.youtube.com/watch?v=_p1PKfZqoGg
Title: Re: Boyajians Star Updates And Discussion
Post by: savuporo on 08/05/2017 03:16 AM
Without even trying to catch up with all the videos and updates between, can someone summarize TL;DR version of what the current observations have shown and what the plausible hypotheses are?
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 08/05/2017 06:20 AM
Without even trying to catch up with all the videos and updates between, can someone summarize TL;DR version of what the current observations have shown and what the plausible hypotheses are?

Pretty much anything is still on the table. I don't think our understanding of the star is much different from what it was when the strange behaviour was first noticed.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/05/2017 08:09 AM
Without even trying to catch up with all the videos and updates between, can someone summarize TL;DR version of what the current observations have shown and what the plausible hypotheses are?

Pretty much anything is still on the table. I don't think our understanding of the star is much different from what it was when the strange behaviour was first noticed.

I wanted to ask you and anyone else what did you think of the latest Bruce Gary's theory expressed via that latest Fredric Parker video I posted?
Title: Re: Boyajians Star Updates And Discussion
Post by: high road on 08/05/2017 08:33 AM
Without even trying to catch up with all the videos and updates between, can someone summarize TL;DR version of what the current observations have shown and what the plausible hypotheses are?

Pretty much anything is still on the table. I don't think our understanding of the star is much different from what it was when the strange behaviour was first noticed.

I wanted to ask you and anyone else what did you think of the latest Bruce Gary's theory expressed via that latest Fredric Parker video I posted?

You probably mean the sinusoidal curve? Seems like you could draw any random curve through the data at this point. Far too few data points to say anything.

Between this, the get-rich-quick fundraising vid and not pronouncing 'periodicity' correctly, Fred's not exactly  scoring high on credibility. He wants to be first to predict the stars behaviour, by working through any theory of what it could be.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/05/2017 08:38 AM
Without even trying to catch up with all the videos and updates between, can someone summarize TL;DR version of what the current observations have shown and what the plausible hypotheses are?

Pretty much anything is still on the table. I don't think our understanding of the star is much different from what it was when the strange behaviour was first noticed.

I wanted to ask you and anyone else what did you think of the latest Bruce Gary's theory expressed via that latest Fredric Parker video I posted?

You probably mean the sinusoidal curve? Seems like you could draw any random curve through the data at this point. Far too few data points to say anything.

Between this, the get-rich-quick fundraising vid and not pronouncing 'periodicity' correctly, Fred's not exactly  scoring high on credibility. He wants to be first to predict the stars behaviour, by working through any theory of what it could be.

Yes I was put off by that fund raising video especially as I thought it was just a standard flux update video as that's how it looked. TBH I am getting to the point where I am just using his videos as a quick way of displaying Bruce Gary's data and that's all. So thanks for your thoughts on the sinusoidal curve.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/05/2017 06:25 PM
Lengthy explanation for the detrending which was due to an equipment issue and that the current detrending is only a temporary fix to be replaced by a more nuanced response. By the way it looks like another shallow dip so far.

Quote
[Orig: Aug 5, 2017]
 
Hi everyone,
 
Past few days have been very productive at LCO. First, some notes on the data pipeline, and the aforementioned "detrending".
 
Background: A second set of 40cm telescopes became available at TFN and OGG at the end of June. It wasn't too long after when we found that one of the new cameras had a hot pixel landing on/near our science target. This is bad because the way we add up all the light in a circular aperture around the star to measure the star's brightness.  If you have a hot pixel within this circular aperture, this contributes to your count, but this contribution is not real (aka, from the star), so your measurements will be all goofed up.
 
After discussing with LCO science support, we went for the easy fix and changed our LCO scheduling requests to apply a shift in the telescope pointing void this hot pixel interfering with the data. We were initially happy with this result, but after a couple weeks we noticed that at the same time we changed the request to shift the pointing, some of the comparison stars had shifted ever so slightly dimmer or brighter compared to the pre-pointing shift observations. We confirmed that this shift in comparison star brightness was not real, i.e., astrophysical, by having independent checks with other data sets to confirm they were constant (courtesy of B. Gary @HAO and J. swift @Thacher). So this indicates that the shift in comparison star brightness was due to the change in telescope pointing: our target (and the comparison stars) were now falling on a different part of the detector.  In a perfect world, the variable response across the detector should be mitigated with standard calibration frames (darks, flats, and biases).  In practice, it does a good job, but at not the precision level we desire.  This introduced our need to "detrend" the data taken during this time (the issue we are experiencing is somewhat analogous to a "meridian flip" (Google it for details) within an observing session.). 
 
For now, we have decided to detrend using a very simple linear model that is dependent on the target's (X, Y) position on the chip. This choice on detrending parameters (X,Y position) was determined most effective based on the considerable improvement in the Bayesian information criterion (BIC) for the comparison stars.  This solution is acceptable, but not necessarily the best.  So, long story short, LSU graduate student Tyler Ellis is working on the best way to treat the data that needs detrending using Gaussian Processes, which essentially will allow for corrections using little or no assumptions from the user.  When we have a solution we are happy with (and all methods converge), he will post a write up on the process.   
 
In the meantime, as of July 24, 2017 we decided to change the pointing back to the "normal" pre-shift position, which can be handled in the regular data pipeline. This means we have meaningful, science quality data immediately.  The data taken during July with the pointing shift will eventually be at this level, but we need to work out the details described above. Going back to the pre-shift pointing also means that there is a chance for the camera to land the target on a hot pixel (the original issue), but we have found the actual amount of unusable data due to this is only ~5%, a loss that is acceptable for the time being given the pros of this strategy.
 
To sum it up, the graph below is data taken from May to today.  It shows the data using the simple linear detrending on X,Y position, and to mitigate any lingering trends, we also only use comparison stars close in proximity to the science target on the camera.   NB, the pointing shift happened from ~50-80 on the x-axis on this graph. Data to the left of ~50 and to the right of ~80 are taken using the same settings.       
 
Are we going for a dip? Whatever you do take care of your shoes! #PhishQuotesForScience.   
         
~Tabby and team

http://www.wherestheflux.com/single-post/2017/08/05/Dip-update-49n
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/06/2017 06:12 PM
The dip continues, now almost one percent.

http://www.wherestheflux.com/single-post/2017/08/06/Dip-update-50n
Title: Re: Boyajians Star Updates And Discussion
Post by: high road on 08/07/2017 07:11 AM
Lengthy explanation for the detrending which was due to an equipment issue and that the current detrending is only a temporary fix to be replaced by a more nuanced response. By the way it looks like another shallow dip so far.

Quote
[Orig: Aug 5, 2017]
 
To sum it up, the graph below is data taken from May to today.  It shows the data using the simple linear detrending on X,Y position, and to mitigate any lingering trends, we also only use comparison stars close in proximity to the science target on the camera.   NB, the pointing shift happened from ~50-80 on the x-axis on this graph. Data to the left of ~50 and to the right of ~80 are taken using the same settings.       
 
Are we going for a dip? Whatever you do take care of your shoes! #PhishQuotesForScience.   
         
~Tabby and team

http://www.wherestheflux.com/single-post/2017/08/05/Dip-update-49n

Even data points before day 50 shift between update 48 and 49, and points continue to shift between update 49 and 50. Would be interesting to know how that works.

Bruce Gary has now superimposed his long term dimming trend over Taby's team's data. With about 0.5% dimming per 100 days, it'll take a few more months to see if this curve is accurate.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/07/2017 07:36 AM
Lengthy explanation for the detrending which was due to an equipment issue and that the current detrending is only a temporary fix to be replaced by a more nuanced response. By the way it looks like another shallow dip so far.

Quote
[Orig: Aug 5, 2017]
 
To sum it up, the graph below is data taken from May to today.  It shows the data using the simple linear detrending on X,Y position, and to mitigate any lingering trends, we also only use comparison stars close in proximity to the science target on the camera.   NB, the pointing shift happened from ~50-80 on the x-axis on this graph. Data to the left of ~50 and to the right of ~80 are taken using the same settings.       
 
Are we going for a dip? Whatever you do take care of your shoes! #PhishQuotesForScience.   
         
~Tabby and team

http://www.wherestheflux.com/single-post/2017/08/05/Dip-update-49n

Even data points before day 50 shift between update 48 and 49, and points continue to shift between update 49 and 50. Would be interesting to know how that works.

Bruce Gary has now superimposed his long term dimming trend over Taby's team's data. With about 0.5% dimming per 100 days, it'll take a few more months to see if this curve is accurate.

If you mean all the points I didn't think they had applied their more nuanced detrending yet and that it was still being worked on?
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/07/2017 07:02 PM
Quote
Dip update 51/n
August 7, 2017
[Orig: Aug 7, 2017]
 
Hi everyone,
 
Here are the nightly averages from May to now. Weather was not great last night at TFN, but we did end up getting a little bit of data, albeit under poor conditions. The telescopes at OGG made up for it though, leading to a measurement pretty much dead on with the TFN measurement, but with much smaller errors due to better conditions and a factor of 4 more measurements.
       
~Tabby and team

http://www.wherestheflux.com/single-post/2017/08/07/Dip-update-51n
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/08/2017 01:06 AM
https://www.youtube.com/watch?v=423BgSueSmA
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/08/2017 06:58 PM
I wonder if we are finally going to get one of those massive dips from the Kepler data.

Quote
Dip update 52/n - Welcome Skara Brae!
August 8, 2017
[Orig: Aug 8, 2017]
 
Hi everyone,
 
This new dip is named Skara Brae.  As of last night, it is about as deep as Celeste, but still a smidgen shallower than Elsie.     
 
Much to do -- more later!
       
~Tabby and team

http://www.wherestheflux.com/single-post/2017/08/08/Dip-update-52n---Welcome-Skara-Brae
Title: Re: Boyajians Star Updates And Discussion
Post by: high road on 08/09/2017 09:54 AM
Without even trying to catch up with all the videos and updates between, can someone summarize TL;DR version of what the current observations have shown and what the plausible hypotheses are?

Pretty much anything is still on the table. I don't think our understanding of the star is much different from what it was when the strange behaviour was first noticed.

I wanted to ask you and anyone else what did you think of the latest Bruce Gary's theory expressed via that latest Fredric Parker video I posted?

You probably mean the sinusoidal curve? Seems like you could draw any random curve through the data at this point. Far too few data points to say anything.

Between this, the get-rich-quick fundraising vid and not pronouncing 'periodicity' correctly, Fred's not exactly  scoring high on credibility. He wants to be first to predict the stars behaviour, by working through any theory of what it could be.

Yes I was put off by that fund raising video especially as I thought it was just a standard flux update video as that's how it looked. TBH I am getting to the point where I am just using his videos as a quick way of displaying Bruce Gary's data and that's all. So thanks for your thoughts on the sinusoidal curve.

Bruce Gary has modified his curve to include the sinusoid, which is no long a sinusoid. It correlates nicely with Tabby's team's data, but I have not yet seen it compared to a previous 'chaotic' measurement, which was the point IIRC. I don't know if that previous 'chaos' (sic) was in his own measurements in 2016, which simply does not contain enough data to do any comparison, or in the Kepler data.

http://www.brucegary.net/ts/
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/09/2017 10:01 AM
Latest Fredric Parker video. Not sure how I feel about them both having preexisting theories and then presenting the data.

https://www.youtube.com/watch?v=dx9JNcwlcoQ
Title: Re: Boyajians Star Updates And Discussion
Post by: TakeOff on 08/09/2017 10:08 AM
What uncertainty do the error bars in the graphs in these videos represent? The uncertainty of what, and how is it quantified?
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/09/2017 10:40 AM
What uncertainty do the error bars in the graphs in these videos represent? The uncertainty of what, and how is it quantified?

With Bruce Gary you're probably best off looking on his site linked to above.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/09/2017 08:15 PM
Even by its standards the star did something very odd last night as explained in this new update. Also they touch on the long term dimming as well.

Quote
Dip update 53/n
August 9, 2017
[Orig: Aug 9, 2017]
 
Hi everyone,
 
Two graphs to share on the data from last night. The first is the nightly averages, the overall brightness is still down (I have removed the two recent TFN points that had large errors due to poor transparency):

Quote
But something very interesting happened in the early part of last night, as you can see below in the  hourly averages for the past couple days (the color of the data points are the same as above for TFN and OGG):

Quote
At the time TFN started taking observations (blue points), the flux was way down(!!); and it continued to change quite significantly over the course of a couple hours.  At the end of the TFN visibility window, it had returned to the same level of brightness from the previous day, and this continued for the time it was observed at OGG.  This short term variability was also independently detected by colleagues observing at the TJO telescope in Spain, so the chances are very good that it is real (not a problem with the data).  Unfortunately what we saw didn't last long, only a couple of hours. But we don't have any coverage just before it, from 94.1-94.3 on this x-axis, so we could only guess to what happened during that time: did we catch it on the way up from a quick, big drop, or was the event more shallow and gradual?         
 
 
I have been reminded that its probably a good idea to note that the data shown here are normalized to unity.  Normalizing to unity shows the depths of the dips plus any long term dimming trends that may be occurring, which is what we care about anyway (the total amount of stuff is between us and the star). We will need a lot more data (when the star is not dipping) to address this long term dimming properly, and at this point its best to avoid such speculation. 
 
More later!
       
~Tabby and team

http://www.wherestheflux.com/single-post/2017/08/09/Dip-update-53n
Title: Re: Boyajians Star Updates And Discussion
Post by: moreno7798 on 08/09/2017 08:33 PM
Latest Fredric Parker video. Not sure how I feel about them both having preexisting theories and then presenting the data.

https://www.youtube.com/watch?v=dx9JNcwlcoQ

I think that what Bruce Gary's long term accelerating dimming may mean is that there are two separate sets of events happening. The first is a long term dimming happening at a steady pace. This could possibly be caused by the star itself - wild guesses may include the star exhausting its fuel at an unprecedented rate. Something that may have started centuries or millennia ago and we're just now looking at the final stages of it. The second event is the  short term dimming events that cause the star to sharply dip intermittently. What causes this is anyone's guess. Although it is possible that both events are linked. Perhaps, the short term dimming events are the cause of the star's long term dimming. Again, how the short term dimming may be linked to the long term dimming is anyone's guess. If you go with the disk of debris theory, then the short term dimming makes sense but the long term dimming does not make sense. If you go with the (very long shot) artificial structures theory, then you could think of a scenario where a cloud of power collecting satellites has been slowly accumulating over the centuries (long term dimming) around the star with the occasional massive space station passing in front of the star (short term dips).
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/09/2017 11:49 PM
https://www.youtube.com/watch?v=suhTAaLxmJw
Title: Re: Boyajians Star Updates And Discussion
Post by: high road on 08/10/2017 08:02 AM
Even by its standards the star did something very odd last night as explained in this new update. Also they touch on the long term dimming as well.

I thought it was not so much "very odd", but "caught in the act". IIRC, either Tabby's team or Parker has said of one of the previous two dips that it's possible they could have missed the 'deep' part of the dip, because those happen on a matter of hours, like normal exoplanet crossovers do. Probably Parker, because I think he was comparing the data of Tabby's team with Kepler data to predict the upcoming measurements. Something he's far more likely to do than Tabby's team.

Any idea where I could find the Thacher data Parker shows in his last vid?

I think that what Bruce Gary's long term accelerating dimming may mean is that there are two separate sets of events happening. The first is a long term dimming happening at a steady pace. This could possibly be caused by the star itself - wild guesses may include the star exhausting its fuel at an unprecedented rate. Something that may have started centuries or millennia ago and were are looking at the final stages of it. The second event is the  short term dimming events that cause the star to sharply dip intermittently. What causes this is anyone's guess. Although it is possible that both events are linked. Perhaps, the short term dimming events are the cause of the star's long term dimming. Again, how the short term dimming may be linked to the long term dimming is anyone's guess.

That has been the state of affairs for a few months now. There is considerable debate about how reliably the current data can be extrapolated to say whether it is accelerating, and whether the dimming and/or acceleration will last for the coming decade and a half.

Quote
If you go with the disk of debris theory, then the short term dimming makes sense but the long term dimming does not make sense. If you go with the (very long shot) artificial structures theory then you could think of a scenario where a slow cloud of power collection satellites has been accumulated over the centuries (long term dimming) around the star with the occasional massive space station passing in front of the star (short term dips).

Yeah, maybe a list of natural explanations and the problems with them might be in order at this point. All that's needed for the dust theory to explain the long term dimming is a long term source of dust.

As for artificial hypotheses: the big space station theory only works if there are many of them out in the Oort cloud of Tabby's star. That's the only way they can pass across the star so slowly and so often. And you still have to find a solution for the problem of the lack of IR radiation.

An alternative is not a space station, but a cloud of space stations, power satellites and ships in orbit around one or more planets or some other industrial hubs. So an entire industrial base, getting progressively denser towards the center. Such a cloud of ships would have an strong motivation to radiate the heat away from the ecliptic and our field of view, because there it would just be reflected by all the other space stations. Plus, the cloud would never look exactly the same from our point of view, which might explain why the shape of the dips might turn out to never repeat.

A third hypothesis is that we're looking at star lifting, and the dips are just the star lifting infrastructure and associated sun spot(s), not moving at the same speed as the star because star lifting infrastructure doesn't need orbital speed to avoid falling into the star. This explains the lack of heat flux because the hydrogen might not be getting used locally (in space and/or time).

All in all, more data is needed. A comparison between al the different observatories looking for different wavelengths would reveal more than just adding more data of the same observatories, IMO.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/10/2017 09:12 AM
Quote
Milo Janus @moveoverbutter

What might nested dipping imply

Tabetha Boyajian @tsboyajian
Replying to @moveoverbutter
Perhaps two clumps of stuff at a time at crossing the LOS. Or changes in density of a single clump

https://mobile.twitter.com/tsboyajian/status/895425511404355584
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/10/2017 11:53 AM
Bruce Gary now showing dip down close to 1%.

http://www.brucegary.net/ts/
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/10/2017 08:39 PM
Quote
Dip update 54/n
August 10, 2017
[Orig: Aug 10, 2017]
 
Hi everyone,
 
Here are the nightly averages since May, and the hourly averages for TFN on MJD 57974 showing the quick big dip described in the last post. The latest measurements show signs of recovery, but its not over yet.
 
More later!
       
~Tabby and team

http://www.wherestheflux.com/single-post/2017/08/10/Dip-update-54n
Title: Re: Boyajians Star Updates And Discussion
Post by: Mongo62 on 08/11/2017 02:11 AM
This video of Fredric Parker's series of videos is a must-see.

He offers a very interesting hypothesis of the type of material causing the long-term dimming.

https://www.youtube.com/watch?v=SacixTlIj00
Title: Re: Boyajians Star Updates And Discussion
Post by: Stan-1967 on 08/11/2017 02:48 AM
So it's aliens then? 

I do not yet feel my place in the universe has been altered, despite the conclusion of the youtube clip.

On a serious note, it seems like the earth based observations lack the needed continuity or cadence to take good measurements during deep dip events.   Gathering good data during these events may be key to solving the entire question of what is happening.   Until that happens, I doubt anyone will be convinced with the current data from the Kickstarter telescope effort.  Kepler gathered dozens of high quality data points each day.  The kickstarter effort delivers 1 or 2 observations per day. ( weather permitting)  Better than nothing, but possibly not enough.

I do think that at some point, probably within the next 18 month, if serious explanations from within the astronomical community have not solved this problem, and ETI is still left standing, as per the trends noted in the latest youtube clip from the prior post, this start may justify a much bigger observation effort, possible even orbital assets.



Title: Re: Boyajians Star Updates And Discussion
Post by: hop on 08/11/2017 07:01 AM
Until that happens, I doubt anyone will be convinced with the current data from the Kickstarter telescope effort.  Kepler gathered dozens of high quality data points each day.  The kickstarter effort delivers 1 or 2 observations per day. ( weather permitting)  Better than nothing, but possibly not enough.
The cadence is actually quite a bit higher than that, the data points on the plots Boyajian posts are mostly time averaged. The star is also being monitored by SWIFT and a number of other ground based observers.

In any case, the main point of the kickstarter funded observations is monitoring, so other observatories can be brought into action when the star does something interesting. When the first post Kepler dip was detected, a lot of big telescopes with sensitive spectrographs took data (presumably also in the second and current dip). Nothing from that has been published yet, but whatever the results are, they should narrow the range of possible solutions significantly.

There are also Spitzer observations planned for Aug 16, and there's potential to get DD time if there's a dip while it's in Spitzers viewing zone.

Title: Re: Boyajians Star Updates And Discussion
Post by: high road on 08/11/2017 07:38 AM
The point of Tabby's monitoring campaign is to find predictable behaviour so she can book better telescopes when she expects to see something interesting.

This video of Fredric Parker's series of videos is a must-see.

He offers a very interesting hypothesis of the type of material causing the long-term dimming.

https://www.youtube.com/watch?v=SacixTlIj00

All I see is his own data saying it's too early to call anything. Without the distraction of the two horizontal lines (which don't "perfectly" contain the data at all because it starts above it and drops significantly below it), I would normalize that with either a straight line starting near the bottom of the "W" on the left towards the knee before the vertical drop. Indicative of dust. But to fit the data better, I'd have to draw a curve rising to about 3/22/2017 and dropping afterwards. Indicative of whatever is blocking the light not being homogenous and maybe even of no permanent acceleration of the dimming.

Taking two arbitrary points and comparing them is quick and dirty for a reason: it's only reliable if the standard deviation in the data is negligable compared to it's long term trend, and that isn't the case here.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/11/2017 07:49 AM
I believe that a primary reason for this campaign is to bolster her case through data to book time on observatories like HST & JWST etc. She's already been granted time on Spitzer.

As to the video to be fair to him he never mentions aliens once, but I suspect there will be a lot of people who will dispute his conclusions about the material being solid.
Title: Re: Boyajians Star Updates And Discussion
Post by: KelvinZero on 08/11/2017 01:03 PM
Im certainly not in favour of the aliens hypothesis. I just wanted to mention one alien idea I have never seen discussed. It just doesn't fit anywhere else. It is a total flight of fantasy.

Perhaps primitive alien life could evolve Dyson swarms without technology. That could explain how you could have a Dyson swarm around one star that never populates neighbours even after millions of years.

Im imagining an evolutionary pathway like: Europa ocean life -> evolves towards surface where more power -> evolves foliage that can withstand vacuum -> evolves seed launchers to leapfrog propagation through roots -> constant exchange of genetic material with other icy worlds -> evolves solar sail abilities -> exponential growth to become Dyson swarm.

I think such a life form would have some really clear affect on spectrum though, just as photosynthesis has a clear affect on the spectrum of earth.
Title: Re: Boyajians Star Updates And Discussion
Post by: moreno7798 on 08/11/2017 01:06 PM
The point of Tabby's monitoring campaign is to find predictable behaviour so she can book better telescopes when she expects to see something interesting.

This video of Fredric Parker's series of videos is a must-see.

He offers a very interesting hypothesis of the type of material causing the long-term dimming.

https://www.youtube.com/watch?v=SacixTlIj00

All I see is his own data saying it's too early to call anything. Without the distraction of the two horizontal lines (which don't "perfectly" contain the data at all because it starts above it and drops significantly below it), I would normalize that with either a straight line starting near the bottom of the "W" on the left towards the knee before the vertical drop. Indicative of dust. But to fit the data better, I'd have to draw a curve rising to about 3/22/2017 and dropping afterwards. Indicative of whatever is blocking the light not being homogenous and maybe even of no permanent acceleration of the dimming.

Taking two arbitrary points and comparing them is quick and dirty for a reason: it's only reliable if the standard deviation in the data is negligible compared to it's long term trend, and that isn't the case here.

He does say that "...the difference between the "V" band and the "C" band are statistically negligible...". He goes on to say that the difference is 2.90% in the V-Band vs. 2.60% in the B-Band.

If anything, the only thing that is needed is a bit more time and data. If the variability between the bands remain constant for the next 9 months, then we could assume there is a good case for Bruce Gary's statements. I, for one, believe that BG's 9-month dataset is sufficiently long enough for the formulation of his theory.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/11/2017 01:29 PM
Im certainly not in favour of the aliens hypothesis. I just wanted to mention one alien idea I have never seen discussed. It just doesn't fit anywhere else. It is a total flight of fantasy.

Perhaps primitive alien life could evolve Dyson swarms without technology. That could explain how you could have a Dyson swarm around one star that never populates neighbours even after millions of years.

Im imagining an evolutionary pathway like: Europa ocean life -> evolves towards surface where more power -> evolves foliage that can withstand vacuum -> evolves seed launchers to leapfrog propagation through roots -> constant exchange of genetic material with other icy worlds -> evolves solar sail abilities -> exponential growth to become Dyson swarm.

I think such a life form would have some really clear affect on spectrum though, just as photosynthesis has a clear affect on the spectrum of earth.

I don't think it's a good idea with this star to favour or disfavour any hypothesis at this point in time. Professor Boyajian has indicated that really all the cards are still in play at this time.

I've been myself foolish enough to favour some ideas over others in the past and in retrospect I can hold up my hands and say that was an ill informed standpoint to take.

I'd like to ask a question is anyone aware if these brief but deep spikes in the overall dips have been noted before or was this recent occurrence the first time one has been caught in the act so to speak?
Title: Re: Boyajians Star Updates And Discussion
Post by: high road on 08/11/2017 03:00 PM
Formulating ideas is good. Launching hypotheses based on several months of data and trying to project future measurements based on what you would expect under this or that theory is a great way to oust or improve flawed hypotheses in an early stage. There's never a point where there's enough data to eliminate the last lingering doubts.

Drawing conclusions based on bad statistics because the data does not, or at least not clearly, support your data is quite bad however. The horizontal lines don't match the data, nor does the horizontal curve even approach a normalized graph of the data.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/11/2017 03:18 PM
Formulating ideas is good. Launching hypotheses based on several months of data and trying to project future measurements based on what you would expect under this or that theory is a great way to oust or improve flawed hypotheses in an early stage. There's never a point where there's enough data to eliminate the last lingering doubts.

Drawing conclusions based on bad statistics because the data does not, or at least not clearly, support your data is quite bad however. The horizontal lines don't match the data, nor does the horizontal curve even approach a normalized graph of the data.

Well certainly not off of one random AAVSO observer. Not to insult any of the amateur observers who take part in it, but it's not going to match the kind of data quality that Professor Boyajian has access to.

Am I being overly cynical if I suggest that claim might have been added to that video to get more views?
Title: Re: Boyajians Star Updates And Discussion
Post by: as58 on 08/11/2017 06:09 PM
Formulating ideas is good. Launching hypotheses based on several months of data and trying to project future measurements based on what you would expect under this or that theory is a great way to oust or improve flawed hypotheses in an early stage. There's never a point where there's enough data to eliminate the last lingering doubts.

Drawing conclusions based on bad statistics because the data does not, or at least not clearly, support your data is quite bad however. The horizontal lines don't match the data, nor does the horizontal curve even approach a normalized graph of the data.

Well certainly not off of one random AAVSO observer. Not to insult any of the amateur observers who take part in it, but it's not going to match the kind of data quality that Professor Boyajian has access to.

Am I being overly cynical if I suggest that claim might have been added to that video to get more views?

He sure seems to be cherry-picking data to fit his conclusions. Furthermore, even if we accept that the long-term is similar in B and V bands, his conclusion that the occulting material is solid isn't, well, solid. For example, claims that gas or "chemicals" would necessarily cause more dimming in the B band is nonsense.
Title: Re: Boyajians Star Updates And Discussion
Post by: moreno7798 on 08/11/2017 07:25 PM
Formulating ideas is good. Launching hypotheses based on several months of data and trying to project future measurements based on what you would expect under this or that theory is a great way to oust or improve flawed hypotheses in an early stage. There's never a point where there's enough data to eliminate the last lingering doubts.

Drawing conclusions based on bad statistics because the data does not, or at least not clearly, support your data is quite bad however. The horizontal lines don't match the data, nor does the horizontal curve even approach a normalized graph of the data.

Well certainly not off of one random AAVSO observer. Not to insult any of the amateur observers who take part in it, but it's not going to match the kind of data quality that Professor Boyajian has access to.

Am I being overly cynical if I suggest that claim might have been added to that video to get more views?

I wouldn't dismiss Bruce Gary's data. Dr. Boyajian was confident enough in his results that she used Gary's data to verify corrections in the detrending. So obviously she has some degree of confidence in his results:

Lengthy explanation for the detrending which was due to an equipment issue and that the current detrending is only a temporary fix to be replaced by a more nuanced response. By the way it looks like another shallow dip so far.

Quote
[Orig: Aug 5, 2017]
 
Hi everyone,
 
Past few days have been very productive at LCO. First, some notes on the data pipeline, and the aforementioned "detrending".
 
Background: A second set of 40cm telescopes became available at TFN and OGG at the end of June. It wasn't too long after when we found that one of the new cameras had a hot pixel landing on/near our science target. This is bad because the way we add up all the light in a circular aperture around the star to measure the star's brightness.  If you have a hot pixel within this circular aperture, this contributes to your count, but this contribution is not real (aka, from the star), so your measurements will be all goofed up.
 
After discussing with LCO science support, we went for the easy fix and changed our LCO scheduling requests to apply a shift in the telescope pointing void this hot pixel interfering with the data. We were initially happy with this result, but after a couple weeks we noticed that at the same time we changed the request to shift the pointing, some of the comparison stars had shifted ever so slightly dimmer or brighter compared to the pre-pointing shift observations. We confirmed that this shift in comparison star brightness was not real, i.e., astrophysical, by having independent checks with other data sets to confirm they were constant (courtesy of B. Gary @HAO and J. swift @Thacher). So this indicates that the shift in comparison star brightness was due to the change in telescope pointing: our target (and the comparison stars) were now falling on a different part of the detector.  In a perfect world, the variable response across the detector should be mitigated with standard calibration frames (darks, flats, and biases).  In practice, it does a good job, but at not the precision level we desire.  This introduced our need to "detrend" the data taken during this time (the issue we are experiencing is somewhat analogous to a "meridian flip" (Google it for details) within an observing session.). 
 
For now, we have decided to detrend using a very simple linear model that is dependent on the target's (X, Y) position on the chip. This choice on detrending parameters (X,Y position) was determined most effective based on the considerable improvement in the Bayesian information criterion (BIC) for the comparison stars.  This solution is acceptable, but not necessarily the best.  So, long story short, LSU graduate student Tyler Ellis is working on the best way to treat the data that needs detrending using Gaussian Processes, which essentially will allow for corrections using little or no assumptions from the user.  When we have a solution we are happy with (and all methods converge), he will post a write up on the process.   
 
In the meantime, as of July 24, 2017 we decided to change the pointing back to the "normal" pre-shift position, which can be handled in the regular data pipeline. This means we have meaningful, science quality data immediately.  The data taken during July with the pointing shift will eventually be at this level, but we need to work out the details described above. Going back to the pre-shift pointing also means that there is a chance for the camera to land the target on a hot pixel (the original issue), but we have found the actual amount of unusable data due to this is only ~5%, a loss that is acceptable for the time being given the pros of this strategy.
 
To sum it up, the graph below is data taken from May to today.  It shows the data using the simple linear detrending on X,Y position, and to mitigate any lingering trends, we also only use comparison stars close in proximity to the science target on the camera.   NB, the pointing shift happened from ~50-80 on the x-axis on this graph. Data to the left of ~50 and to the right of ~80 are taken using the same settings.       
 
Are we going for a dip? Whatever you do take care of your shoes! #PhishQuotesForScience.   
         
~Tabby and team


A point about BG's latest theory on the V/B bands dataset...

Perhaps we should not look at the V/B band dataset as one that "Needs to be normalized" to be valid. If you take the two measurements as separate datasets, then, as Gary mentioned, all that matters is that each dataset is unchanging and that they are close enough that the difference is "Negligible". But I do think that more data and time will tell the true tale. If both the V/B bands data remain the same for a number of more months, then it would not be easy to explain it with the dust and debris theory. Assets in space would be needed to obtain more precise Interferometry but I think you can get pretty good results with large datasets that could yield enough confidence in the variability's margin of error.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/11/2017 07:42 PM
Talking of Interferometry this is regarding an email from Professor Boyajian, via Reddit.

Quote
Tyler and I will be traveling to Mount Wilson Observatory this weekend for an observing run at the CHARA Array.

http://www.chara.gsu.edu/public/tour-overview

Apparently this is second only to the Keck in its field.
Title: Re: Boyajians Star Updates And Discussion
Post by: high road on 08/11/2017 10:14 PM
Formulating ideas is good. Launching hypotheses based on several months of data and trying to project future measurements based on what you would expect under this or that theory is a great way to oust or improve flawed hypotheses in an early stage. There's never a point where there's enough data to eliminate the last lingering doubts.

Drawing conclusions based on bad statistics because the data does not, or at least not clearly, support your data is quite bad however. The horizontal lines don't match the data, nor does the horizontal curve even approach a normalized graph of the data.

Well certainly not off of one random AAVSO observer. Not to insult any of the amateur observers who take part in it, but it's not going to match the kind of data quality that Professor Boyajian has access to.

Am I being overly cynical if I suggest that claim might have been added to that video to get more views?

I wouldn't dismiss Bruce Gary's data. Dr. Boyajian was confident enough in his results that she used Gary's data to verify corrections in the detrending. So obviously she has some degree of confidence in his results:

the random observer is David Lane. But yeah, data is data. The more observations, the better.

Quote
Lengthy explanation for the detrending which was due to an equipment issue and that the current detrending is only a temporary fix to be replaced by a more nuanced response. By the way it looks like another shallow dip so far.

Quote
[Orig: Aug 5, 2017]
 
Hi everyone,
 
Past few days have been very productive at LCO. First, some notes on the data pipeline, and the aforementioned "detrending".
 
Background: A second set of 40cm telescopes became available at TFN and OGG at the end of June. It wasn't too long after when we found that one of the new cameras had a hot pixel landing on/near our science target. This is bad because the way we add up all the light in a circular aperture around the star to measure the star's brightness.  If you have a hot pixel within this circular aperture, this contributes to your count, but this contribution is not real (aka, from the star), so your measurements will be all goofed up.
 
After discussing with LCO science support, we went for the easy fix and changed our LCO scheduling requests to apply a shift in the telescope pointing void this hot pixel interfering with the data. We were initially happy with this result, but after a couple weeks we noticed that at the same time we changed the request to shift the pointing, some of the comparison stars had shifted ever so slightly dimmer or brighter compared to the pre-pointing shift observations. We confirmed that this shift in comparison star brightness was not real, i.e., astrophysical, by having independent checks with other data sets to confirm they were constant (courtesy of B. Gary @HAO and J. swift @Thacher). So this indicates that the shift in comparison star brightness was due to the change in telescope pointing: our target (and the comparison stars) were now falling on a different part of the detector.  In a perfect world, the variable response across the detector should be mitigated with standard calibration frames (darks, flats, and biases).  In practice, it does a good job, but at not the precision level we desire.  This introduced our need to "detrend" the data taken during this time (the issue we are experiencing is somewhat analogous to a "meridian flip" (Google it for details) within an observing session.). 
 
For now, we have decided to detrend using a very simple linear model that is dependent on the target's (X, Y) position on the chip. This choice on detrending parameters (X,Y position) was determined most effective based on the considerable improvement in the Bayesian information criterion (BIC) for the comparison stars.  This solution is acceptable, but not necessarily the best.  So, long story short, LSU graduate student Tyler Ellis is working on the best way to treat the data that needs detrending using Gaussian Processes, which essentially will allow for corrections using little or no assumptions from the user.  When we have a solution we are happy with (and all methods converge), he will post a write up on the process.   
 
In the meantime, as of July 24, 2017 we decided to change the pointing back to the "normal" pre-shift position, which can be handled in the regular data pipeline. This means we have meaningful, science quality data immediately.  The data taken during July with the pointing shift will eventually be at this level, but we need to work out the details described above. Going back to the pre-shift pointing also means that there is a chance for the camera to land the target on a hot pixel (the original issue), but we have found the actual amount of unusable data due to this is only ~5%, a loss that is acceptable for the time being given the pros of this strategy.
 
To sum it up, the graph below is data taken from May to today.  It shows the data using the simple linear detrending on X,Y position, and to mitigate any lingering trends, we also only use comparison stars close in proximity to the science target on the camera.   NB, the pointing shift happened from ~50-80 on the x-axis on this graph. Data to the left of ~50 and to the right of ~80 are taken using the same settings.       
 
Are we going for a dip? Whatever you do take care of your shoes! #PhishQuotesForScience.   
         
~Tabby and team


A point about BG's latest theory on the V/B bands dataset...

Perhaps we should not look at the V/B band dataset as one that "Needs to be normalized" to be valid. If you take the two measurements as separate datasets, then, as Gary mentioned, all that matters is that each dataset is unchanging and that they are close enough that the difference is "Negligible". But I do think that more data and time will tell the true tale. If both the V/B bands data remain the same for a number of more months, then it would not be easy to explain it with the dust and debris theory. Assets in space would be needed to obtain more precise Interferometry but I think you can get pretty good results with large datasets that could yield enough confidence in the variability's margin of error.

Bruce Gary hasn't made any new suggestions that I'm aware of. Do you have a link or do you mean Fredric? In the latter case, arbitrarily drawing lines on a set of data above your highest and below the lowest data point and calling it stable is bad statistics. You could do the same for Tabby,s data, BG data and call the long term dimming trend nonsense. None of the datasets are 'unchanging'.

Now if he would have come up with a theory why there seems to be a maximum difference between the two bands, that would have been an interesting idea. Still limited data to be making that call, but very good for further investigation.
Title: Re: Boyajians Star Updates And Discussion
Post by: Star One on 08/11/2017 10:16 PM
I wonder if they have any particular theories they want to test with the CHARA array.
Title: Re: Boyajians Star Updates And Discussion
Post by: moreno7798 on 08/12/2017 07:00 AM