Author Topic: Boyajians Star Updates And Discussion  (Read 118083 times)

Offline Star One

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Boyajians Star Updates And Discussion
« Reply #880 on: 10/18/2017 04:05 PM »
Another paper

Modelling the KIC8462852 light curves: compatibility of the dips and secular dimming with an exocomet interpretation
M. C. Wyatt, R. van Lieshout, G. M. Kennedy, T. S. Boyajian

(Accepted for publication in MNRAS)
Quote
This paper shows how the dips and secular dimming in the KIC8462852 light curve can originate in circumstellar material distributed around a single elliptical orbit (e.g., exocomets). The expected thermal emission and wavelength dependent dimming is derived for different orbital parameters and geometries, including dust that is optically thick to stellar radiation, and for a size distribution of dust with realistic optical properties. We first consider dust distributed evenly around the orbit, then show how to derive its uneven distribution from the optical light curve and to predict light curves at different wavelengths. The fractional luminosity of an even distribution is approximately the level of dimming times stellar radius divided by distance from the star at transit. Non-detection of dust thermal emission for KIC8462852 thus provides a lower limit on the transit distance to complement the 0.6au upper limit imposed by 0.4day dips. Unless the dust distribution is optically thick, the putative 16% century-long secular dimming must have disappeared before the WISE 12micron measurement in 2010, and subsequent 4.5micron observations require transits at >0.05au. However, self-absorption of thermal emission removes these constraints for opaque dust distributions. The passage of dust clumps through pericentre is predicted to cause infrared brightening lasting 10s of days and dimming during transit, such that total flux received decreases at wavelengths <5micron, but increases to potentially detectable levels at longer wavelengths. We suggest that lower dimming levels than seen for KIC8462852 are more common in the Galactic population and may be detected in future transit surveys.
I've only skimmed it, but it seems like a significant step to building a coherent model for the "exocomet" (in the broad sense of dusty things in elliptical orbit) theories that accounts for the IR observations, long term variability and dips.

Note although Dr Boyajian is a co-author, this is not the anticipated paper on the recent dips. From the last kickstarter update
Quote
Lastly, since activity has seemed to subside for a little bit, we have plans to move forward and publish the dip announcement paper, so stay tuned!

Though it’s an elaborate explanation, having looked through this paper, I favour Bruce Gary’s theory as it explains all aspects of this star’s behaviour which this paper doesn’t.
« Last Edit: 10/18/2017 04:06 PM by Star One »

Offline Star One

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Boyajians Star Updates And Discussion
« Reply #881 on: 10/18/2017 04:37 PM »
New article. You will need to translate it from its native German.

https://abenteuer-astronomie.de/wunderstern-kic8462852-wiederholt-sich-das-muster-der-einbrueche/

Quote
Dip update 105/n
October 18, 2017
[Orig: Oct 18, 2017]
 
Hi everyone,
 
Below is the light curve as of a few hours ago. Note I have removed the TFN point from the night before because it didn't constrain diddly. 
 
More later,
 
~Tabby and team

http://www.wherestheflux.com/single-post/2017/10/18/Dip-update-105n

By the way Bruce Gary has taken down his webpage.
« Last Edit: 10/18/2017 04:47 PM by Star One »

Online high road

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Re: Boyajians Star Updates And Discussion
« Reply #882 on: 10/26/2017 08:35 PM »
That's strange. His predictions are lasting longer than usual ;-)

http://www.wherestheflux.com/single-post/2017/10/26/Dip-update-110n

Offline Star One

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Boyajians Star Updates And Discussion
« Reply #883 on: 10/29/2017 08:52 AM »
Bruce Gary has updated his site with 10/29 data and a new note:

Quote
The last g'-mag is the brightest measured during the past 12 months! I predict that during the first week of November this brightening will reach a level ~ 1.5 % higher than during the past summer months. The brightening currently underway was predicted on this web page Oct 10, and ~ 3 months ago in an e-mail by a colleague. Paper#3 will explain why it is brightening so fast right now (really simple once it's explained). We are hoping to submit paper#1 to MNRAS next week, and a week later post it at arXiv (and at this web page)."

http://www.brucegary.net/ts4/
« Last Edit: 10/29/2017 08:53 AM by Star One »

Offline Star One

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Re: Boyajians Star Updates And Discussion
« Reply #884 on: 11/04/2017 10:33 AM »
Bruce Gary has made some revisions to his model. He cut his 1.5% prediction down to .8%.

http://www.brucegary.net/ts4/

Offline M.E.T.

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Re: Boyajians Star Updates And Discussion
« Reply #885 on: 11/04/2017 12:37 PM »
Bruce Gary has made some revisions to his model. He cut his 1.5% prediction down to .8%.

http://www.brucegary.net/ts4/

Star One. I know you have followed this star's saga quite closely since the beginning.

Would you be willing to give a summary of the latest prevailing theory, including what Bruce Gary's so called prediction is all about, and what it means for the likely solution to the mystery? With the dimming events seeming to be on hold for the time being, news on the star seems to have faded away (hehe) lately.

While the dimming events were in full swing, I heard everything from the E.T. hypothesis having been disproven, to massive ringed planets bigger than Jupiter, to an invisible brown dwarf and everything inbetween.

Essentially, what is being suggested as the reason behind the lack of any further 15-22% dips subsequent to Kepler's observations? And is an E.T. solution at all still on the cards?

Offline Star One

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Re: Boyajians Star Updates And Discussion
« Reply #886 on: 11/04/2017 01:52 PM »
Bruce Gary has made some revisions to his model. He cut his 1.5% prediction down to .8%.

http://www.brucegary.net/ts4/

Star One. I know you have followed this star's saga quite closely since the beginning.

Would you be willing to give a summary of the latest prevailing theory, including what Bruce Gary's so called prediction is all about, and what it means for the likely solution to the mystery? With the dimming events seeming to be on hold for the time being, news on the star seems to have faded away (hehe) lately.

While the dimming events were in full swing, I heard everything from the E.T. hypothesis having been disproven, to massive ringed planets bigger than Jupiter, to an invisible brown dwarf and everything inbetween.

Essentially, what is being suggested as the reason behind the lack of any further 15-22% dips subsequent to Kepler's observations? And is an E.T. solution at all still on the cards?

Bruce Gary favours a rather complicated natural solution. That is a Brown Dwarf with rings that is also orbited by three Neptune class planets. These planets in turn have icy moons that sublimate material as the whole system approaches Boyajian’s star. The Brown Dwarf is in an highly eccentric orbit around Boyajian’s star, and the Brown Dwarf has an orbit that lasts 4.3 years.

Offline M.E.T.

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Re: Boyajians Star Updates And Discussion
« Reply #887 on: 11/04/2017 02:18 PM »
Bruce Gary has made some revisions to his model. He cut his 1.5% prediction down to .8%.

http://www.brucegary.net/ts4/

Star One. I know you have followed this star's saga quite closely since the beginning.

Would you be willing to give a summary of the latest prevailing theory, including what Bruce Gary's so called prediction is all about, and what it means for the likely solution to the mystery? With the dimming events seeming to be on hold for the time being, news on the star seems to have faded away (hehe) lately.

While the dimming events were in full swing, I heard everything from the E.T. hypothesis having been disproven, to massive ringed planets bigger than Jupiter, to an invisible brown dwarf and everything inbetween.

Essentially, what is being suggested as the reason behind the lack of any further 15-22% dips subsequent to Kepler's observations? And is an E.T. solution at all still on the cards?

Bruce Gary favours a rather complicated natural solution. That is a Brown Dwarf with rings that is also orbited by three Neptune class planets. These planets in turn have icy moons that sublimate material as the whole system approaches Boyajian’s star. The Brown Dwarf is in an highly eccentric orbit around Boyajian’s star, and the Brown Dwarf has an orbit that lasts 4.3 years.

Thank you.

Online MikeAtkinson

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Re: Boyajians Star Updates And Discussion
« Reply #888 on: 11/04/2017 02:57 PM »
Bruce Gary favours a rather complicated natural solution. That is a Brown Dwarf with rings that is also orbited by three Neptune class planets. These planets in turn have icy moons that sublimate material as the whole system approaches Boyajian’s star. The Brown Dwarf is in an highly eccentric orbit around Boyajian’s star, and the Brown Dwarf has an orbit that lasts 4.3 years.

It seems to me a problem with that model is the large number of free parameters: size of brown draft, eccentricity of its orbit; size, number and inclination of the ring; number, size and inclination of the Neptune class planets; number, size and composition of the icy moons; details of the sublimation and dust forming processes; details of the dust removal processes; and probably others that I have not thought of.

With so many free parameters a model like that can be made to fit the observations (particularly the patchy observations that we have so far). The model is also so complex that clear and precise predictions are probably not possible from it, witness the latest prediction, it was:

Quote
The last g'-mag is the brightest measured during the past 12 months! I predict that during the first week of November this brightening will reach a level ~ 1.5 % higher than during the past summer months. The brightening currently underway was predicted on this web page Oct 10, and ~ 3 months ago in an e-mail by a colleague. Paper#3 will explain why it is brightening so fast right now (really simple once it's explained). We are hoping to submit paper#1 to MNRAS next week, and a week later post it at arXiv (and at this web page)."

and is now:

Quote
The brightening continues to be consistent with a leveling off at a modest 0.8 % above the summer low (when all the dips were occurring).

While I think that something like Bruce Gary's model is most likely to be correct, I think that the details are most likely wrong and that just by studying the light curves (at the current level of observation) it will take decades to pin down the details of such a model.

Offline Stan-1967

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Re: Boyajians Star Updates And Discussion
« Reply #889 on: 11/04/2017 03:31 PM »
I'm looking forward to the paper being published.  This theory has the initial look of positing real explanations that are testable.  B. Gary is also realistic in stating that this is "a good starting place for new understandings".  I do think the theory has some problems, but they can at least be tested.

From the online link:  http://www.brucegary.net/ts4/  bold & underlined are my emphasized sections

     3) Something orbits KIC846 with a period of ~ 1600 days (ie., at an average distance of 3.0 AU).
     4) Things orbit the above object, and their dust produces the short-term dips. The object being orbited must be a "massive object."
            Why? Because a set of objects can't be in an identical orbit this close to each other; only the 5 Lagrange regions permit stability in orbits with the same period.
     5) The things that orbit the 1600-day "massive object" have orbits that extend on each side by "an orbit circumference fractional amount" = (400 days / 2)  / 1600 days = ~ 1/16.
            Note: 400 days is the length of the "1-year fade feature" (which is actually closer to 1.2 years).
     6) Assuming the objects that orbit the "massive object" are within the massive object's Hill sphere, the massive object must have a mass of  > 14 × M_Jupiter.
            Note: Anything more massive than ~ 13 × M_Jupiter is a candidate for being a brown dwarf (BD); hereafter I'll refer to the "massive object" as a BD.
     7) The dips are produced by dust (that could be configured as a tail, a coma or a ring system) that originates from moon-size objects orbiting either the BD or planets that orbit the BD.
           Why? Because the "gravity well" for the BD, or any orbiting planets, will be too deep! Comets produce dust tails because their gravity wells are shallow.


My criticism's & thoughts:
RE: #6.   If the BD is this large, & approaches the star within 3AU, it should produce an easily detectable angular velocity shift far in excess of 1m/s ( detectable limit)   It also seems to me that in order for the dimmings to be caused by this, from our viewpoint, the BD's orbital plane has to be closely aligned with our line of sight.  It doesn't have to be exact, just enough for the posited dust envelope to occult the star, or brighten our view, depending on alignment.

RE: #7.  All of my problems are with this section.  On the surface, it seems like Bruce Gary, & his unknown contributor, have taken the original "comet swarm" theory, & placed the comets into a elliptical orbit around the BD to get the needed periodicity.  It's contrived, but it solves the key periodicity problem & given the nature of this puzzle, it's an acceptable starting point.  However from there, I think it breaks down. 

He notes that comets produce dust/gas tails due to low gravity of the parent body, but because these comets are within the Hill sphere of the BD, the form a "cloud" or dust ring that is responsible for the dimmings/brightenings.  I don't see how this can be a stable configuration over billions, or even millions of years.   He posits the BD also likely have planets or moon sized objects in orbit.  These would sweep up or eject the smaller comet bodies over the life of the system.   The BD system should not have stable condition for swarms of comets at the suggested age of this star.  Even if it was a newly captured extrasolar BD, this seems highly unlikely.

Furthermore, his theory seems to also suggest the moons themselves may behave as huge comets when inside the frost line of the star.  Comets lack the gravity to capture the dust & gas ejected from the surface, moons do not.   The larger objects in the BD system would at best, have very thin expanding/contracting atmospheres as they orbit the BD & host star.   Any small objects/comets orbiting the BD would be more like Jupiter family comets, with very depleted comas due to the orbit of the BD being relatively close to the star for the entire orbit.  Comets orbiting the BD are not going to be some analog of new long period Oort/Kuiper belt objects like Hale-Bopp.  Think of comet Temple 1 or Encke.  The depleted volatiles leave a surface high in dust, & jets are rare & not significant on the order needed by B.Gary's theory to occur.  Even moons high in volatiles orbiting the BD would at best be like a Ceres or Vega type asteroid.   

In a sense, B.Gary & contributor's theory places an anachronistic protoplanetary BD system into orbit around a main sequence F-type mid life star.    How does that happen?  I don't think it does under any wild circumstance.
« Last Edit: 11/04/2017 05:55 PM by Stan-1967 »

Offline Star One

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Re: Boyajians Star Updates And Discussion
« Reply #890 on: 11/04/2017 03:42 PM »
I was rather hoping Bruce Gary & his mysterious collaborator would have published their paper by now.

Offline RotoSequence

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Re: Boyajians Star Updates And Discussion
« Reply #891 on: 11/04/2017 10:45 PM »
I was rather hoping Bruce Gary & his mysterious collaborator would have published their paper by now.

We've been through several iterations of Bruce Gary predictions. His prediction times have only become accurate recently, while the magnitudes are still in a state of constant flux. Time will tell if future predictions continue to hold.

Offline Mongo62

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Re: Boyajians Star Updates And Discussion
« Reply #892 on: 11/12/2017 02:25 PM »

Offline Star One

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Re: Boyajians Star Updates And Discussion
« Reply #893 on: 11/16/2017 09:01 PM »
Bruce Gary’s paper see what you think?

https://arxiv.org/abs/1711.04205

Offline JasonAW3

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Re: Boyajians Star Updates And Discussion
« Reply #894 on: 11/20/2017 10:23 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.

 Interesting thought.  A brown dwarf in relatively close orbit MIGHT account for the periodic dimming, but the long term dimming is still a bit of a mystery.
My God!  It's full of universes!

Offline Stan-1967

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Re: Boyajians Star Updates And Discussion
« Reply #895 on: 11/23/2017 07:22 AM »
Bruce Gary’s paper see what you think?

https://arxiv.org/abs/1711.04205

He & the co-author also posted this one.
https://arxiv.org/pdf/1711.07472.pdf

Bruce Gary affirmed my problems with his BD theory, as well as the many other proposed causes in the last page:

"KIC8462 is a very complicated system, as evidenced by
the many categories of brightness variability. Any
model will necessarily have to be similarly complicated.
This translates to a greater need for observations lasting
many years, and especially during our predicted repeat
of the U-shaped and dip fades in 2021.
As models are developed for natural structures that can
account for the observed fades (such as ring systems and
comas) there will be a parallel effort needed for the
development of the physical mechanisms that can
produce such structures."


Offline Star One

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Boyajians Star Updates And Discussion
« Reply #896 on: 11/24/2017 07:18 PM »
The star is either returning to normal brightness levels, it’s been above normal for a little while, or going into another dip depending on who you listen to. There’s been some debate I’ve seen as to whether the brightening events are as significant as the dips in understanding this star.

You can see visually what I am talking about in this most recent posting by professor Boyajian.

http://www.wherestheflux.com/single-post/2017/11/24/Dip-update-119n
« Last Edit: 11/24/2017 07:23 PM by Star One »

Offline Star One

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Re: Boyajians Star Updates And Discussion
« Reply #897 on: 11/25/2017 08:41 AM »
Bruce Gary now talking of a shallow dip of 0.34%.

http://www.brucegary.net/ts5/

Offline Star One

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Boyajians Star Updates And Discussion
« Reply #898 on: 11/30/2017 09:01 PM »
A note by Bruce Gary at the top of Bruce Garys Web Page says
Quote
"A recent dip reached a depth of 0.45 ± 0.10 % and has stayed at this depth for almost a week. I'm puzzled (as usual) by this fickle star! "

http://www.brucegary.net/ts5/
« Last Edit: 11/30/2017 09:04 PM by Star One »

Offline Star One

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Boyajians Star Updates And Discussion
« Reply #899 on: 12/07/2017 08:01 PM »
New research note published by Bruce Gary & Rafik Bourne.

KIC 8462852: Potential Repeat of the Kepler Day 1540 Dip in 2017 August

http://iopscience.iop.org/article/10.3847/2515-5172/aa9edd/meta
« Last Edit: 12/07/2017 08:02 PM by Star One »

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