I am betting that it is a very large star in a binary system with a brown dwarf.

We may never know for sure--let's see what the pundits come up with.

The dimming seems to be achromatic:
http://www.astronomerstelegram.org/?read=10406
This would support the ETI hypothesis.

The talk is, that the spectra taken during the current dimming of Boyajian's Star appear uniform in strength, throughout (achromatic). If these initial observations are born out by more detailed analyses, the extraterrestrial megastructure hypothesis would be strengthened, by the process of elimination.

The more credible natural astrophysical explanations for the star's extraordinary behavior all depend on a very dusty environment. These explanations involve either 1.) A huge swarm of massive comets orbiting the star, or 2.) Concentrated lumps of dust in the interstellar medium, which intermittently pass between the star and Earth.

Either of these should produce spectra favoring the red end of the spectrum with weakening at the blue end caused by absorption by the dust.

Does the initial findings say anything about that 1 theory I heard in the livestream from a few days ago, about how maybe a planet crashed into the star a while ago. That might have made the star abnormally brighter, and it's been irregularly trending down in brightness back to normal levels?

If the uniform color holds this would rule out the planet eating, if I understand it right, for the brief dips.

Latest rumor is that there is "color" after all :-(

Yes, we'll have to wait to see what comes of hints of possible excess infrared radiation. Without further details, we can only say that this might be due to dust, or it could be caused by a megastructure absorbing the star's energy and re-radiating it in the infrared. Both are physical mechanisms that have been widely discussed with respect to Boyajian's Star.

In the meantime we have preliminary spectra from the 2 meter Liverpool Telescope at La Palma, Canary Islands, and from the 3.5 meter telescope at Apache Point Observatory, in New Mexico. These show no significant departure from achromaticity, in the bands 5800--9400 Angstroms (visual through infrared) and 3890--4010 Angstroms ( ultraviolet and violet), respectively.

A continuing failure to find spectrum changes in KIC 8462852 during dimming, as compared to the non-dimmed spectra, would argue for very large, solid objects (too large to be planets) in orbit of the star, instead of dust and debris.

today as I was walking to work...& watching a Venus & Mars on the clear sky...thinking about celestial bodies...1 idea came to my mind:

1. advanced civilization more advanced than us, should have populated "stable Lagrange points L4 & L5"...so much like what "L5 society" has been proposing!
so if half orbit is about 700-750d, or 1400-1500d full-orbit for an Earth-size planet in habitable zone of Tabby star (1.5 Sol)...than those objects could be seen 220-250d before a main planet & 220-250d after a main planet...
some similar discrepancy have been seen in previous observations with smaller dips in dimming of that star!
2. postulation that every 700-750d something dims the star, can be explained with populating L3 Lagrange point...which is not only possible, but plausible by any of the advanced species (humans included, when we start to populate the Space!)
even some advanced K2 civilizations might be possible to:
a) bring another planet to L3 Lagrange point & put it in stable orbit inside habitable zone of Tabby's star
b) restart magnetic core of the planet (like Mars) to make it habitable again for aliens
3. postulation of a "ring size Dyson swarm" is plausible, but making so large structure wouldn't be "efficient" & therefore not intelligent from advanced civilization...
or that function of a structure of that size eludes my intellect (which is also plausible)?! but still, a question remains: why would someone make a ring with radius of 1.8AU?! ;)

proposition to SETi team:
1. if Apr 2015 was missed as a main goal of a big dim of the Tabby star, then I urge all SETi scientist to look at Tabby star from now till Jan 2016...
2. & if another occurrence is scheduled in May 2017...then some previous observation should be made on Aug & Sep 2016 (7-8m before main dim, when L4 Lagrange points come to viewpoint)!
3. after May 2017, another occurrence of L5 Lagrange point will come in Jan&Feb 2018!
ruling out that there aren't any objects in L4 & L5 Lagrange points will also confirm that (most likely) there isn't an advanced civilization in Tabby star system...
;)

references:
- https://www.newscientist.com/article/dn28191-citizen-scientists-catch-cloud-of-comets-orbiting-distant-star/
- http://sites.psu.edu/astrowright/2015/10/15/kic-8462852wheres-the-flux/

Yes, it was predicted...as we know, Tabby star is something like 50% larger than Sun, so their habitable zone (to life similar to our) is on 1500d year rotation!

So either they go something in L3 or the really have made a Dyson ring?!

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non-profit org. Play4Life in Zagreb, Croatia, EU

Anybody else read this?

http://www.iflscience.com/space/new-hypothesis-for-tabbys-star-suggests-a-ringed-planet-and-lots-of-asteroids/

Would this idea be shot down by achromatic spectra? Would the ringed planet be too small?

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Had a look at the Ballesteros, et al. paper to which the article refers. It seems to require a ringed planet with a radius 0.3 times that of Boyajian's Star. A planet anywhere near this large is not to be expected.

Planets more than a little larger than Jupiter are compacted by their own gravity, and grow denser, not larger. A body nearly one third the size of an F class star would be able to fuse hydrogen at its core, and so be a star, not a planet. No such star has been found to exist near KIC 8462852.

Such a star would reveal itself in a number of ways: 1.) We should probably be able to see it. 2.) Its gravity would cause a substantial wobble in the motion of Boyajian's Star. 3.) It should emit enough heat to have been detected in the infrared. None of these things has occurred.

Had a look at the Ballesteros, et al. paper to which the article refers. It seems to require a ringed planet with a radius 0.3 times that of Boyajian's Star. A planet anywhere near this large is not to be expected.

Planets more than a little larger than Jupiter are compacted by their own gravity, and grow denser, not larger. A body nearly one third the size of an F class star would be able to fuse hydrogen at its core, and so be a star, not a planet. No such star has been found to exist near KIC 8462852.

Such a star would reveal itself in a number of ways: 1.) We should probably be able to see it. 2.) Its gravity would cause a substantial wobble in the motion of Boyajian's Star. 3.) It should emit enough heat to have been detected in the infrared. None of these things has occurred.

Thank you,
I was thinking the planet would have to be very large, so the idea seemed problematic. If I had to hazard a guess, I'd put money on a natural explanation that we just don't understand yet.

Assuming for the sake of argument that this was some kind of artificial structure however, isn't the lack of infrared in spectra a problem?
Or is it possible that an advanced civilization could have materials that are efficient enough that they would reflect very little in that band? For example, even the heat itself is being redirected/used somehow? Sorry, just thinking out loud.

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It's said that one of the prime indicators of an extraterrestrial megastructure would be excess infrared radiation. The use of a substantial portion of the energy of a star would, by the laws of thermodynamics, as we understand them, inevitably produce a good deal of waste heat as a byproduct.

In another forum, I suggested something quite similar to the idea you raised. The energy of the star could be reflected and redirected by very high efficiency mirrors. We've already begun work on such reflectors, called 'perfect mirrors'. Of course nothing is really perfect, but a very high efficiency of reflection would leave so little excess energy that we might not be able to detect it.

I had the idea that the energy might be redirected back into the star, for the purpose of modifying it, so as to extend its life. An F class star like KIC 8462852 has a rather short time on the life-supporting main sequence, compared to our Sun. Probably too short a time for intelligent life to have evolved there.

There seems to be a new dip going on. If so, that would rule out the Super-Saturn-and -Trojans model
See https://www.reddit.com/r/KIC8462852/.

None of the currently popular explanations for the dipping, and/or long term fading of Boyajian's Star seem satisfactory.

A giant ringed planet with huge clouds of Trojan asteroids at the fore and aft positions along its orbit? Besides, as you note, not matching well with the observed behavior of the star, such a planet would need to be nearly a third the size of the star. That would make it an honest-to-goodness, hydrogen fusing star, itself, not a planet. No such star is seen near KIC 8462852.

A cloud of gas and dust interposed between us and the star? Highly remarkable that this should affect only one star, instead of many. Besides this, none of the irregularities in sodium, expected of an interstellar cloud capable of causing the dips, have been found in recent spectroscopy.
Intrinsic variations in Boyajian's Star, itself? Experience with a great many main sequence stars, in their prime of life, indicates that these stars are very consistent in their stable light output.

Withall, the situation reminds me of the history of astronomy. When it was thought that the Sun and planets all orbited around the Earth, fantastic systems of complex epicycles (circles upon circles) had to be devised to account for the observed motions of the planets. The whole thing became a creaking mess, and finally fell apart in the face of the much simpler Sun-centered system we still use today.

The tendency in science has been to leave the explanations involving extraterrestrial intelligence as a last resort, when all natural explanations fall short. Fine, up to that point, but not past it.

There seems to be a new dip going on. If so, that would rule out the Super-Saturn-and -Trojans model
See https://www.reddit.com/r/KIC8462852/.

The new drop in light output from the star KIC 8462852, which began several days ago, continues at this time. It has nearly reached the minus 2 percent level, and may, for all we know, continue to decline. The larger the decrease in brightness, the more that can be learned about what makes the star behave in such a peculiar way.

In the meantime, we have indications that the shorter wavelengths were slightly dimmed in the May 19th dip, relative to the longer ones. This did not follow the pattern expected from dusty debris in that star system, though. It's effect was to small for that.

It might be that we are seeing the effects of nano-machines, so called 'smart dust', in that distant star system. These would have presumably been less numerous that expected for dust particles, at the time of the observations, and so dimmed the blue light less than ordinary dust would have.

If this scenario is true, we should eventually see confirmation that the May 19th dip is characterized by gradually lessening of dimming at the shorter wavelengths. At all wavelengths there should consistently be substantially less dimming than would be the case if dusty debris were the cause.

This article could explain some things..

The “alien megastructure” star that has been puzzling us for the past few years might have a more ordinary explanation: an orbiting Saturn-like planet, complete with wobbling rings. In 2015, a group led by Tabetha Boyajian, then of Yale University, found that a star called KIC 8462852 had dimmed several times over a few years in a way they couldn’t explain. The star had been observed by the Kepler space telescope between 2009 and 2013 as it hunted for exoplanets by staring at a patch of sky. When a planet passes in front of a star, an event called a transit, the light intensity dips slightly and then returns to normal. But KIC 8462852, since dubbed Tabby’s star, didn’t behave that way, with the ...

https://www.newscientist.com/article/2144869-alien-megastructure-star-may-host-saturn-like-exoplanet/

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Suppose a planet could maintain immense rings, large enough to block out up to 22 percent of the star's light, which is what would be required in the case of KIC 84622852. The author specifies that this would be a 'close in' planet. This leaves us with the unanswered question: Where is the excess infrared radiation that such a planet, and especially its rings, would be expected to create? The material is close enough to the star to receive substantial stellar radiation, and reradiate it in the infrared. No such excess infrared has been observed at Tabby's Star, and it has been looked for with considerable care.

A planet that big and close to its parent star should also impart a wobble in the star's orbit, leading to a Doppler shift in the star's light. I'm not aware that any such Doppler shift has been detected for KIC8462852.

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It ain't aliens:
https://www.inverse.com/article/36239-tabby-s-star-not-alien-megastructures-new-study-kic-8462852-nasa