Did planet hunter discovered a swarm of comets... Or an alien megastructure?

Planet Hunters X. KIC 8462852 - Where's the Flux?

Quote :

Over the duration of the Kepler mission, KIC 8462852 was observed to undergo irregularly shaped, aperiodic dips in flux down to below the 20% level. The dipping activity can last for between 5 and 80 days. We characterize the object with high-resolution spectroscopy, spectral energy distribution fitting, and Fourier analyses of the Kepler light curve. We determine that KIC 8462852 is a main-sequence F3 V/IV star, with a rotation period ∼ 0.88 d, that exhibits no significant IR excess. In this paper, we describe various scenarios to explain the mysterious events in the Kepler light curve, most of which have problems explaining the data in hand. By considering the observational constraints on dust clumps orbiting a normal main-sequence star, we conclude that the scenario most consistent with the data in hand is the passage of a family of exocomet fragments, all of which are associated with a single previous breakup event. We discuss the necessity of future observations to help interpret the system"

http://www.theatlantic.com/science/archive/2015/10/the-most-interesting-star-in-our-galaxy/410023/

http://www.popsci.com/have-we-detected-alien-megastructures-around-distant-star?src=SOC&dom=fb

Tu lis trop de science-fiction !!

ET don't talk :
http://arxiv.org/abs/1511.01606

Marengo, Hulsebus and Willis, "KIC 8462852 - The Infrared Flux"
http://arxiv.org/abs/1511.07908

Consistent with the cometary hypothesis.

Lisse, Sitko & Marengo "IRTF/SPEX Observations of the Unusual Kepler Lightcurve System KIC8462852"
http://arxiv.org/abs/1512.00121

Possibly the initial stages of a Late Heavy Bombardment-type episode?

Things get a bit weirder:

Schaefer (2016) "KIC 8462852 Faded at an Average Rate of 0.165±0.013 Magnitudes Per Century From 1890 To 1989"
http://arxiv.org/abs/1601.03256

Things get less weird:

KIC 8462852 did likely not fade during the last 100 years
http://arxiv.org/abs/1601.07314

It seems the reported dimming is caused by poor calibration in the data.

An article about this one is up at Centauri Dreams.

Quote :

Bradley Schaefer strongly disputes Hippke’s work, so we haven’t heard the end of this.

Hmmmm.

Also I'm wondering just how much we really know about variability on timescales of centuries (or longer) of various stellar types.

The response from Bradley Schaefer is now up at Centauri Dreams.
Ouch.

Probably discovered periodicity of eclipses in the famous system of KIC 8462852.

http://arxiv.org/pdf/1509.03622v2.pdf Printed 26 January 2016
On the fifth page:
"There is another possible periodicity that is worth discussing briefly. In Table 1, we summarize the times and depths of 10 discrete dips present in the Kepler light curve, also labeled in panel ‘(b)’ – ‘(e)’ of Figure 1. If we examine the two most prominent dips (D1568 and D1520; also see panel ‘(d)’ in Figure 1), we see that they have a separation of 48.8 days. We can also see that the D800 dip (dip #5 in Table 1) is separated from the D1520 dip by 15 of these intervals, if the interval is more precisely defined to be 48.4 days. Furthermore, the very shallow dips early in the Kepler time series at D260 and D360 are very close to 26 and 24 of these 48.4-day cycles from the D1520 dip. The other five identified discrete dips (four of which are very shallow), also listed in Table 1, are about a half cycle out of phase with this period to within ±5% of a cycle. In this exercise, we have neglected the fact that the three most prominent dips in the D1500 region are quite highly structured, and they also have additional minima whose times could have been tagged and included in the analysis. At this time we do not ascribe any particular significance to this period, but it is something to bear in mind as more data on this object become available."
In gratitude article:
"We thank Josh Carter for pointing out the possible 48-day periodicity."
Possible explanations for the periodicity?
1) Artifact handling
2) Unknown type of periodic variable stars
3) Constellation astroengineering objects (like NASA A-train and GEO ring)

Latest update from Hippke et al.

The arXiv paper has now been updated and accepted to the Astrophysical Journal: http://arxiv.org/abs/1601.07314v4

See also this article on Centauri Dreams, which gives an overview of the updates.

And another arXiv paper, Hippke is a co-author.

Lund et al. (2016) "The Stability of F-star Brightness on Century Timescales"
http://arxiv.org/abs/1605.02760

New dimming event on 04 May 2016.
https://m.reddit.com/r/KIC8462852/comments/4ik3d2/apparent_may_4_dimming_of_kic_8462852/?utm_source=mweb_redirect

Light Curve

Schaefer trashes Hippke (and collaborators) again

http://www.centauri-dreams.org/?p=35666

KIC 8462852 Faded Throughout the Kepler Mission
http://arxiv.org/abs/1608.01316

Another star showing weird dips, that has hit the news with predictable "alien megastructure" headlines.

Scaringi et al. "The peculiar dipping events in the disk-bearing young-stellar object EPIC 204278916"
http://arxiv.org/abs/1608.07291

One of the news stories: http://www.sciencealert.com/researchers-just-found-a-second-dyson-sphere-star

That's some remarkable efficiency, finding our second Dyson sphere before we've even found the first

Sirius with the burns  

Though this system seems distinct from the other Upper Scorpius "dippers" (Ansdell et al.), it is still far easier to explain than KIC 8462852. A precessing disk would make it similar to the other dippers, but a cometary origin is also not unreasonable.

This star is set for reobservation in Campaign 15 (barring any further instrument failures), so more quantitative models may be possible in future.

Sirius_Alpha wrote:

KIC 8462852 Faded Throughout the Kepler Mission
http://arxiv.org/abs/1608.01316

https://carnegiescience.edu/news/our-galaxy%E2%80%99s-most-mysterious-star-even-stranger-astronomers-thought

Simon and Montet’s findings caused a stir in August, when they were posted on a preprint server while their paper was being reviewed. Now their work is now accepted for publication by The Astrophysical Journal

Next round!

Hippke et al. "Sonneberg plate photometry in two colors for KIC 8462852: No dimming between 1934 and 1995"
https://arxiv.org/abs/1609.09290

From the abstract:

Quote :

The data cover the years 1934 to 1995 and are very evenly sampled between 1956 and 1995. In both colors, we find the star to be of constant brightness within 0.033mag/century (~3%). The previously claimed dimming is inconsistent with these data at the ∼5σ-level, however the recently reported modest dimming of ~3% in the Kepler data is not inconsistent with these data. We have also searched for periodicities and yearly trends in the data and find none within our limits of ~10% per year.

Wonder what the response to this one will be...

https://arxiv.org/abs/1612.06121

Mysterious eclipses in the light-curve of KIC8462852 : a possible explanation

It is found that it is possible to reproduce the basic features in the light-curve of KIC8462852 with only four objects enshrouded in dust clouds. The fact that they are all on similar orbits and that such models require only a handful of free parameters provide additional support for this hypothesis.
This model provides an alternative to the comet scenario

Secular Dimming of KIC 8462852 Following its Consumption of a Planet
https://arxiv.org/abs/1612.07332

They suggest the system is consistent with the star having recently absorbed a planet within the past few melennia, which would go a long way to explaining the various photometric phenomena we see there, however the likelihood that we would be lucky enough to observe such an event poses the biggest problem.

Why it pose problem? Tabby star has unique behavior, it would be problematic if this behavior was moreregular.

Another event has started
https://twitter.com/tsboyajian/status/865542587087601665

If this holds up, gas and dust clouds appear to be excluded, it would almost have to be solid objects.

Medium Resolution Spectroscopy of Boyajian's Star (KIC 8462852)

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ATel #10405 reports that a several percent dip in the brightness of KIC 8462852 is underway.

We report medium resolution spectroscopy (R=2500) taken with the FRODOSpec fibre fed integral field spectrograph of the 2.0 meter Liverpool Telescope, La Palma obtained on 20th May 2017 starting at 01:20UT. Three 600 second exposures were obtained, giving a total integration time of 1800 seconds. The wavelength range was 5800 - 9400 Angstroms.

The spectrum is compared with a reference spectrum obtained "out of dip" on 4th July 2016 with an identical instrumental setup and exposure time.

In an initial analysis we find no difference between the two spectra apart from in features that are attributable to the expected variable telluric absorption features in the Earth's atmosphere.

Excerpts of the spectra in the region of H-alpha (https://www.dropbox.com/s/u11lv7d5opeo0rr/KIC-halpha.png?dl=0) and the IR Calcium Triplet (https://www.dropbox.com/s/isev1ymggilx4hl/KIC-Ca.png?dl=0) are shown (the different ripples in the two Ca spectra are due to CCD fringing in the detector). Taking the ratio of the two spectra gives standard deviations per pixel of 2 percent of the continuum level in the H-alpha region and 3 percent in the Calcium triplet region, with no evidence of any changes visible between the two epochs in the lines.

We will continue to monitor the object. We would like to thank Drs Klaas Wiersema (Leicester) and Grant Kennedy (Cambridge) for bringing the notification of the current dip to our attention.