Author Topic: Boyajians Star Updates And Discussion  (Read 196149 times)

Offline Star One

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Boyajians Star Updates And Discussion
« Reply #1060 on: 06/27/2018 09:08 AM »
Interesting discussion on that paper here. One initial point raised is why it hasn’t used any data from David Lane. As he points out himself especially as he observed it through the period. I suppose they are driving at that it claims to use all sources and then clearly doesn’t.

https://www.reddit.com/r/KIC8462852/comments/8tzl8f/another_new_paper_the_kic_8462852_light_curve/

Anyway the star might be dipping again, but it’s too early to say.

https://mobile.twitter.com/tsboyajian/status/1011329504139194368
« Last Edit: 06/27/2018 09:16 AM by Star One »

Offline Star One

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Re: Boyajians Star Updates And Discussion
« Reply #1061 on: 06/28/2018 08:21 PM »
Another new paper about this star.

The Variable Wavelength Dependence of the Dipping event of KIC 8462852

Eva Bodman, Jason Wright, Tabetha Boyajian, Tyler Ellis

(Submitted on 22 Jun 2018)

Quote
First observed with the Kepler mission, KIC 8462852 undergoes unexplained dimming events, "dips," on the timescale of days which were again observed from the ground from May to December 2017. Monitored with multi-band photometry by the Los Cumbres Observatory, all four dips of the "Elsie dip family" display clear wavelength dependence. We measure how the wavelength dependence changes over the whole dimming event, including the dimming between the dips and the brightening event (the `blip') which occurs after the dips. We find that a single wavelength dependence does not fit the entire light curve and the dimming occurring between the dips is non-gray and varies in time. Because of the non-gray dimming between the dips, we measure the wavelength dependence of the dips separately and without the extra depth from this dimming. Such measurements yield a different estimate of the wavelength dependence the wavelength dependence of the dips but remains consistent with the previous measurement except for Elsie (the first dip), which is surrounded by dimming with strong wavelength dependence. We find the range of the wavelength dependence variation of the entire 2017 light curve is consistent with optically-thin dust with an average radius of
r<1μ
m and the dust causing just the dips being
r<0.5μ
m. Since the dependence is time-dependent, the dust occulting the star must be heterogeneous in size, composition, or both and the distributions of these properties along the line of sight must change over time.


https://arxiv.org/abs/1806.08842
« Last Edit: 06/28/2018 08:22 PM by Star One »

Offline Alpha_Centauri

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Re: Boyajians Star Updates And Discussion
« Reply #1062 on: 11/07/2018 02:20 PM »
Interesting, possibly another one. The morphology looks very familiar but the depth here is massive.

https://arxiv.org/abs/1811.02265
Quote
VVV-WIT-07: another Boyajian’s star or a Mamajek’s object?

We report the discovery of VVV-WIT-07, an unique and intriguing variable source presenting a sequence of recurrent dips with a likely deep eclipse in July 2012. The object was found serendipitously in the near-IR data obtained by the VISTA Vari- ables in the V ́ıa La ́ctea (VVV) ESO Public Survey. Our analysis is based on VVV variability, multicolor, and proper motion (PM) data. Complementary data from the VVV eXtended survey (VVVX) as well as archive data and spectroscopic follow-up observations aided in the analysis and interpretation of VVV-WIT-07. A search for periodicity in the VVV Ks-band light curve of VVV-WIT-07 results in two tentative periods at P ∼ 322 days and P ∼ 170 days. Colors and PM are consistent either with a reddened MS star or a pre-MS star in the foreground disk. The near-IR spectra of VVV-WIT-07 appear featureless, having no prominent lines in emission or absorption. Features found in the light curve of VVV-WIT-07 are similar to those seen in J1407 (Mamajek’s object), a pre-MS K5 dwarf with a ring system eclipsing the star or, al- ternatively, to KIC 8462852 (Boyajian’s star), an F3 IV/V star showing irregular and aperiodic dips in its light curve. Alternative scenarios, none of which is fully consistent with the available data, are also briefly discussed, including a young stellar object, a T Tauri star surrounded by clumpy dust structure, a main sequence star eclipsed by a nearby extended object, a self-eclipsing R CrB variable star, and even a long-period, high-inclination X-ray binary.

Offline jebbo

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Re: Boyajians Star Updates And Discussion
« Reply #1063 on: 12/03/2018 08:37 AM »
And more ... starting to look like there's a population of objects withe weird dips!

The Little Dippers: Transits of Star-grazing Exocomets?
Quote
We describe EPIC 205718330 and EPIC 235240266, two systems identified in the K2 data whose light curves contain episodic drops in brightness with shapes and durations similar to those of the young "dipper" stars, yet shallower by ~1-2 orders of magnitude. These "little dippers" have diverse profile shapes with durations of ~0.5-1.0 days and depths of ~0.1-1.0% in flux; however, unlike most of the young dipper stars, these do not exhibit any detectable infrared excess indicative of protoplanetary disks, and our ground-based follow-up spectra lack any signatures of youth while indicating these objects as kinematically old. After ruling out instrumental and/or data processing artifacts as sources of the dimming events, we investigate possible astrophysical mechanisms based on the light curve and stellar properties. We argue that the little dippers are consistent with transits of star-grazing exocomets, and speculate that they are signposts of massive non-transiting exoplanets driving the close-approach orbits.

Arxiv paper

--- Tony

Offline Star One

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Boyajians Star Updates And Discussion
« Reply #1064 on: 12/04/2018 09:48 PM »
2018 data update (40/n)
December 4, 2018
[Orig: November 30, 2018]
 
Hello everyone!
 
Today I have a few items to share with y'all.
 
The first is the usual update on the most recent data we have on the star. Just like the last few months, we are not able to detect any significant activity, and the brightness levels remain a bit elevated compared to the pre-Elsie brightness back in 2017 May. Looking ahead, the star is becoming less and less available to us Earthlings as the year progresses. This is simply due to where the Earth is in its orbit around the Sun. In another month or so we will lose sight of the star for a few months. Like previous years, we will monitor it during this time with the Swift space telescope. We propose to observe at a ~3 day cadence, which will be able to detect any large, long lasting event.
 
The second item I wanted to share is a super cool (maybe a bit crazy) idea we had involving the community on the research we do. This idea was inspired by discussions in the star's sub-reddit over the past few years, where the topics have covered practically everything but astronomical image analysis. Then I asked myself, why stop there?! So I submitted a proposal to be a partner in the Las Cumbres Education Program - and it was accepted! [See here, and the links within, for details.]
 
What this means is that over the next year we will have access to the Las Cumbres 0.4m telescope network to monitor the star on a ~weekly cadence. Data taken with this program (as well as all other LCO Ed programs) are available to the public immediately. Our group will be 'united' through reddit, where we will provide support and share our results and experiences collecting and analyzing photometric data with other members. We are still setting things up on the social media side, so check back soon if you are interested in being involved. Our program is open to *anyone*, you just have to have access to a computer and the internet. This will be fun!!
 
All the best,
 
~Tabby and team

http://www.wherestheflux.com/single-post/2018/12/04/2018-data-update-40n
« Last Edit: 12/04/2018 09:49 PM by Star One »

Offline Star One

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Re: Boyajians Star Updates And Discussion
« Reply #1065 on: 12/04/2018 10:07 PM »
Further to the above.

Have Astronomers Found Another "Alien Megastructure" Star?

Quote
In 2010, the Vista Variables in the Via Lactea (VVV) survey began its project of creating a three-dimensional map of variable stars in the vicinity of the Milky Way’s center. As part of the project, astronomer Roberto Saito of the Federal University of Santa Catarina scoured the telescope’s data for eruptive outbursts from the hundreds of millions of monitored stars. But the most notable thing he found was not an outburst at all—it was a star that grew mysteriously dim over several days in 2012. He and his colleagues reported their findings in a recently published paper in the Monthly Notices of the Royal Astronomical Society.
Known as VVV-WIT-07, the star appears to be much older and redder than our sun, although the amount of interstellar dust between our solar system and the star’s home closer to the galactic center makes exact classification and distance measurements very difficult. What is certain is that in the summer of 2012, the object's brightness faded slightly for 11 days, then plummeted over the following 48 days, suggesting that something blocked more than three quarters of the star’s light streaming toward Earth. But what could that “something” be?

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