The merged and improved (?) KIC 8462852 thread

Yes, I'd recommend watching that as well although I did have to turn on the subtitles as I found the narrator's pronunciation distracting. One key point is that more data is required.

 

Then I'll take two.
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Yes, he has a speech impediment exactly like the guy on the Big Bang Theory. You get used to it pretty quick. I am at the point were I almost think it adds to his vids now. He puts out a lot of quality videos about topics like this one.

 

More observations of the Tabby's star add to the weirdness but do not clear up the mystery:

http://phys.org/news/2016-08-latest-tabby-star-weirdness.html#jCp

More information at http://www.universetoday.com/130213/tabbys-star-megastructure-mystery-continues-intrigue/ and https://arxiv.org/pdf/1608.01316v1.pdf

 

A planetesimal colliding with an object in that stars outer system--that seems to be the idea now.

 

That's still the leading candidate. Capturing several dimming events in as many wavelengths as possible would help disambiguate what is going on.

https://www.newscientist.com/articl...alien-megastructure-star-baffles-astronomers/

 

FG Sagittae, V605 Aquilae and V4334 Sagitarii are just three stars that have rapidly and repeatedly changed luminosity and even position up and down the H-R diagram in the span of a human lifetime. There are other stars with erratic behaviors that are "impossible" based on establishment understanding of stellar evolution. Sirius and Capella were described by ancient writers (Cicero, Horace, Ptolemy, Seneca, et al) as "red." (Seneca described Sirius as "redder than Mars.")

Then Bradley Schaefer had the bad taste to consult photographic plates going back a century showing "Tabby's Star" dimming even more. So naturally the establishment shot the messenger and questioned the evidence.

There are other explanations that do not involve alien megastructures, or vast swarms of dark matter, er, I mean comets. Occultation is not the only mechanism possible.

 

The conventional explanation (that is, non-electric universe) for FG Sagittae, V605 Aquilae and V4334 Sagitarii is late thermal pulse. Bradley Schaefer's methodology means his derived results are of questionable value but we've been over this ground previously. Other writers in antiquity (such as the Chinese) described Sirius as white and the translation of ancient texts is debatable (http://www.armaghplanet.com/blog/the-other-sirius-mystery-red-or-white.html) but perhaps something anomalous happening such as with Sirius A's white dwarf companion Sirius B. However, 2000 years is usually thought way too short a period for a giant to become a white dwarf. The usual estimate is that Sirius B made the transition about 150 Mya. Capella is a four-star system -- one binary pair of two giants and another of two red dwarfs. I suppose at least one of the giants might have exhibited some instability as their stage in development on the giant branch is uncertain but the historical records for Capella ever actually being red are even more debatable than for Sirius.

 

Don't get ahead of yourselves. The most recent arXiv paper is basically the publication of a grad student's dissertation.

More importantly, I suspect it is just the latest example of the increasingly obvious fact that the scientific community has learned to accept a general lack of rigor in the pursuit of most "scientific studies" and that the scientific method ITSELF has become dangerously watered-down by a generation of fly-by-night academics who simply publish as many papers as they can on as many topics as they can knowing good and damn well that nobody is ever going to call them out if their research is full of holes.

 

Well said. For awhile, THE LANCET seemed home for any quck who wouldn't even be allowed a sniff of a JAMA cover.

 

Always excellent points, Crazy Eddie. There's nothing wrong with suggesting a swarm of comets, or an alien megastructure. With any new phenomenon, one must fling out lots of ideas—perhaps even crazy ones—to see if they stick. Still, the "alien megastructure" is too quick a shortcut for me, much like the first pulsars suggesting extraterrestrial intelligence, or the Sun being a god's flaming chariot.

Asbo, out of curiosity (and respecting your breadth of knowledge in the field), would Tabby be similar to HD 12545 (XX Trianguli), or has that possibility already been eliminated?

 

XX Trianguli has an enormous star spot so one sees a regular periodic dimming as the star rotates.
http://www.skyandtelescope.com/astronomy-news/seeing-spots-on-a-red-giant-star-1104201545/
As the large scale dimming of the light curve of Tabby's star doesn't correlate with the star's rotational period, my understanding is that star spots could be eliminated as a cause.

 

So larger sized suns would experience more and larger star spots compared to a sun such as ours?

I am going to go with Star Spots as the reason for the dims of KIC 8462.

 

^"As the large scale dimming of the light curve of Tabby's star doesn't correlate with the star's rotational period, my understanding is that star spots could be eliminated as a cause."

 

I suppose there is a possibility that this is a new phenomenon similar to a flare star perhaps where intense magnetic fields in the stellar atmosphere causing turbulent short-lived super spot activity but it would be strange that super flare brightening would not also occur. Flare stars are also usually red dwarfs.

 

Update - http://arxiv.org/pdf/1608.01316v1.pdf

1. 5.5. A Polar Spot Under certain conditions, a long-lasting spot growing at polar latitudes on the surface of KIC 8462852 could possibly reproduce the long-term light curve observed here. While polar spots have not previously been detected on an F3V dwarf star, they have been observed on the surface of an F9V star, albeit one in a tight (1.15 day) binary with another stellar companion (Strassmeier & Rice 2003). Through Doppler tomography observations, polar spots on more massive stars have been seen to evolve on similar timescales to the flux variability observed here (Roettenbacher et al. 2016). For a polar spot to create the observed decrease in flux in the light curve, the star would need to be at a low enough inclination so that the pole is always visible. Boyajian et al. (2016) measure a rotation period and v sin i of the star and combine these with an estimate of the radius to infer an inclination of 68 ± 29 degrees at 68% confidence, leaving open the possibility that the pole can indeed be observed at all times. If a spot were growing near the polar latitudes of the days. The measured RV of KIC 8462852 in these observations has a scatter of 0.3 km s−1 and each observation has a precision of 0.4 km s−1 . While the data are consistent with no RV variations, continued monitoring could detect the presence of massive companions on wider orbits. High resolution spectra could also be used to probe any evolution in the magnetic activity of the star correlated with the growth or decay of spots.
   
   
2. 6. CONCLUSIONS - Recently, multiple analyses of DASCH photometry have produced conflicting results about the possible detection of a long-term dimming of KIC 8462852 by 0.165 ± 0.013 magnitudes over the 20th century, or 0.152 ± 0.012% yr−1 . The dimming of a star at that rate should be detectable in Kepler data. Here, we analyze monthly Kepler FFI images to search for similar dimming in the FFI light curve of KIC 8462852. We perform aperture photometry on KIC 8462852 and seven nearby comparison stars. We observe that during the first three years of the Kepler mission, the star dimmed at a rate of 0.341±0.041% yr−1 . Over the following 6 months, the star decreased in brightness by 2.5%, then remained at that level for the duration of the primary Kepler mission. This result is not sensitive to the size of the chosen aperture or the particular choice of reference stars. We then compare this result to a similar analysis of other stars of similar brightness on the same detector, as well as stars with similar stellar properties, as listed in the KIC, in the Kepler field. We find that 0.5% of stars on the same detector and 0.7% of stars with similar stellar properties exhibit a long-term trend consistent with that observed for KIC 8462852 during the first three years of the Kepler mission. However, in no cases do we observe a flux decrement as extreme as the 2.5% dip observed in Quarters 12-14 of the mission. The total brightness change of KIC 8462852 is also larger than that of any other star we have identified in the Kepler images. Broadly speaking, the morphology of the light curve is generally consistent with the transit of a cloud of optically thick material orbiting the star. Such a dust cloud could be small enough to evade submillimeter detection in the analysis of Thompson et al. (2016), who place a limit of 7.7 M⊕ of material orbiting KIC 8462852. The breakup of a small body or a recent collision that could produce a cloud of material could also plausibly produce a family of comets that transit the host star together.
3. 
   
4. as one group (Bodman & Quillen 2016), explaining the light curve observed by Boyajian et al. (2016). However, in order to match the observed time of ingress and transit duration, some fine-tuning is required. To explain the transit ingress timescale, the cloud would need to be at impossibly large distances from the star or be slowly increasing in surface density. The flat bottom of the transit would then suggest a rapid transition into a region of uniform density in the cloud, which then continues to transit the star for at least the next year of the Kepler mission. Moreover, such a model does not naturally account for the long-term dimming in the light curve observed in both DASCH and the Kepler FFI data, suggesting that this idea is, at best, incomplete. We strongly encourage further refinements, alternative hypotheses, and new data in order to explain the full suite of observations of this very mysterious object. Facility: Kepler

 

As the abstract of the paper states:

 

http://www.space.com/33674-alien-megastructure-star-just-got-even-weirder.html

KIC 8462852 was observed by NASA's Kepler mission and has become infamous for its bizarre and unprecedented transit signal that was flagged by citizen scientists. Now new research of precision Kepler observations has shown that the overall brightness of the star — unofficially named "Tabby's Star" after astronomer Tabetha S. Boyajian who discovered the peculiar signal — has been decreasing, which poses a new and confusing problem for astronomers trying to understand what the heck is going on.

"Broadly speaking, the morphology of the light curve is generally consistent with the transit of a cloud of optically thick material orbiting the star," Monet and Simon write in their paper. "The breakup of a small body or a recent collision that could produce a cloud of material could also plausibly produce a family of comets that transit the host star together as one group, explaining the light curve..."

has been decreasing....

Normally a cloud will not be thick enough to cause a continual dimming but would create ebbs in the light curve. Go outside sometime on a sunny day and watch the clouds pass in front of the Sun. The clouds will never fully cover the Sun to cause a continual decrease or prolonged decrease in the light curve of the sun but will instead cause ebbs. If the light curve of KIC 8462 is continuing to decrease then perhaps the cloud is comprised of more objects that is causing the decrease as the center of the cloud transits across KIC 8462. If the light curves begin to increase and continue to increase then I would have to say that a large cloud of material possibly a half of a light year in length could be present transiting across KIC 8462.

 

Ahem, http://www.trekbbs.com/threads/the-...c-8462852-thread.276611/page-32#post-11704664

 

What about large cloud of solid material might look like transiting across KIC 8462.

One idea that has not been suggested is that the sudden increase and continual increase of the decreasing light curve of KIC 8462 could possibly be the result of a large ring of material around KIC 8462 that may be titled in such a manner of degrees that from a perspective point of view Kepler is imaging the light curve of KIC 8462 with the inner diameter of the ring as well as the outer diameter of the ring causing less light to be seen.

Basically the distance of the inside diameter of the ring to the outside diameter has become much greater meaning more material might be present in this thicker region of the ring then other sections of the ring that because of the tilt of the ring, would cause the light curve of KIC 8462 to decrease.