2018 March: dip update 9/nMarch 30, 2018[Orig: March 30, 2018] Hi everyone, New data taken the past couple days show that the brightness is back to normal, or perhaps just below normal. Have a great weekend! ~Tabby and team
I asked about that somewhere else, and from what I understand, the rayleigh scattering wavelength for molecular hydrogen and helium is much too high for the observed dimming.
Tabby's latest kickstarter e-mail shares that the latest observations from ELP in West Texas have brightness back up to normal.Apparently, Tabby and Team are treating the March 2018 sequence as two dips, and each will have its own name.
Announcing: Caral-Supe!April 5, 2018[Orig: April 5, 2018] Hi everyone, "Caral-Supe" is now the name for the first dip in March 2018!! It is now labeled on the latest light curve (see below). More on "Caral-Supe": Sticking with the archaeological theme, the ancient city Caral-Supe is one of the earliest sites in the Americas - well over 4000 years old. Also notable is the large number of musical instruments found at the site, and almost no evidence of warfare or human sacrifice. The name of the 2nd dip will be announced early next week, so stay tuned! Best, ~Tabby and team
From what I’ve read online it seems the betting is on Gaia DR 2 showing this star as being closer to Earth than previously estimated.
Quote from: Star One on 04/21/2018 09:38 amFrom what I’ve read online it seems the betting is on Gaia DR 2 showing this star as being closer to Earth than previously estimated.I don't see why. The star was already included in DR 1 parallax catalogue, which showed that it's about as far as expected based on its brightness. It would be surprising if DR 2 changed the distance estimate significantly in either direction and I'm not expecting that Gaia DR2 will help very much in solving the mystery of this star. My feeling from what I've read online is that some people have rather unrealistic expectations about what Gaia can do.
Quote from: as58 on 04/22/2018 06:00 amQuote from: Star One on 04/21/2018 09:38 amFrom what I’ve read online it seems the betting is on Gaia DR 2 showing this star as being closer to Earth than previously estimated.I don't see why. The star was already included in DR 1 parallax catalogue, which showed that it's about as far as expected based on its brightness. It would be surprising if DR 2 changed the distance estimate significantly in either direction and I'm not expecting that Gaia DR2 will help very much in solving the mystery of this star. My feeling from what I've read online is that some people have rather unrealistic expectations about what Gaia can do.The initial release put KIC8462852 significantly but not dramatically closer than the previous estimates.
450pc for #BoyajiansStar from #GaiaDR2
just 4 pc from our spectroscopic plx here (link: https://arxiv.org/pdf/1509.03622.pdf) arxiv.org/pdf/1509.03622…
The WTF paper used an estimate of the line of sight extinction from the colors of the spectrum vs what's expected for an F3 star to get to 450 pc. If there's a 100-year dimming due to line of sight dust (including circumstellar) that should be accounted for in the estimate!
Excited to announce that our paper (1574-day orbit at Boyajian"s Star) was accepted / published at JAAVSO! (link: https://www.aavso.org/apps/jaavso/article/3327/) aavso.org/apps/jaavso/ar…@BoyajiansStar @tsboyajian @Astro_Wright
AbstractObservations of the main sequence F3V star KIC 8462852 (also known as Boyajian’s star) revealed extreme aperiodic dips in flux up to 20% during the four years of the Kepler mission. Smaller dips (< 3%) were also observed with ground-based telescopes between May 2017 and May 2018. We investigated possible correlation between recent dips and the major dips in the last 100 days of the Kepler mission. We compared Kepler light curve data, 2017 data from two observatories (TFN, OGG) which are part of the Las Cumbres Observatory (LCO) network, as well as archival data from the Harvard College Observatory (HCO), Sonneberg Observatory, and Sternberg Observatory, and determined that observations appear consistent with a 1,574-day (4.31-year) periodicity of a transit (or group of transits) orbiting Boyajian’s star within the habitable zone. Comparison with future observations is required to validate this hypothesis. Furthermore, it is unknown if transits that have produced other major dips as observed during the Kepler mission (e.g. D792) share the same orbital period. Nevertheless, the proposed periodicity is a step forward in guiding future observation efforts.
We know from the spectrum seen during the last few dips that the dimming is caused by fine dust. As mentioned in the Deeg et. al. paper the dust particles are too small to resist being blown away by the radiation pressure of the star's light. Whatever is causing the dust needs to be replenishing it on a timescale of days. If the 1574 day period is confirmed to be statistically significant then it is likely that whatever is generating the dust is in that orbit. Assuming that the orbit is somewhat circular the object or objects would be nice and warm most or all of the time. What sort of object can produce that much dust while being in a relatively stable orbit at a distance of 3au? I'd think that even if it was a comet swarm the comets would have shed all the volatiles and become inert long ago.
California high school students from @CdeP will present new data on #TabbysStar at the #aas232 press conference today.Tune in at 11am MDT/12pm CDT: (link: https://aas.org/media-press/aas-press-conference-webcasts) aas.org/media-press/aa…@tsboyajian @LSUphysastro
I know so many want to know in plain English what all this means. If confirmed, a 1574-day periodicity further constrains several potential long-standing causes of the ongoing dips, such as intrinsic variation or dust in the interstellar medium. Simply put, it means there is something in orbit around the star at about 3 AU (within the habitability zone assuming a circular orbit). Furthermore, this paper may lend support to the Boyajian et al. (2018) paper, in which fine dust was identified as a possible cause of the dips. It also adds intrigue to the Boyajian et al. (2016) paper with respect to the observation that many dip separations are multiples of 24.2 days. Interestingly, a 1574-day period is equivalent to 65 even periods of 24.2 days. Furthermore, when you combine orbiting material with century-long dimming and no detected IR excess, it adds more mystery to this star….not less. The fact is, we still don’t know what the source is of such dust. Perhaps a ring of broken comets that are slowly moving into our line of sight thereby dimming the star over decades or even centuries. Or maybe, just maybe, something unnatural. In any case, whatever the cause, this paper should make you want to say "WTF" even more so!
The star KIC 8462852 (Boyajian's Star) displays both fast dips of up to 20% on time scales of days, plus long-term secular fading by up to 19% on time scales from a year to a century. We report on CCD photometry of KIC 8462852 from 2015.75 to 2018.18, with 19,176 images making for 1,866 nightly magnitudes in BVRI. Our light curves show a continuing secular decline (by 0.023 +- 0.003 mags in the B-band) with three superposed dips with duration 120-180 days. This demonstrates that there is a continuum of dip durations from a day to a century, so that the secular fading is seen to be by the same physical mechanism as the short-duration Kepler dips. The BVRI light curves all have the same shape, with the slopes and amplitudes for VRI being systematically smaller than in the B-band by factors of 0.77 +- 0.05, 0.50 +- 0.05, and 0.31 +- 0.05. We rule out any hypothesis involving occultation of the primary star by any star, planet, solid body, or optically thick cloud. But these ratios are the same as that expected for ordinary extinction by dust clouds. This chromatic extinction implies dust particle sizes going down to ~0.1 micron, suggesting that this dust will be rapidly blown away by stellar radiation pressure, so the dust clouds must have formed within months. The modern infrared observations were taken at a time when there was at least 12.4% +- 1.3% dust coverage (as part of the secular dimming), and this is consistent with dimming originating in circumstellar dust.