Is KIC 8462852 (Tabby's Star) Being Eclipsed by Four Dusty Exoplanets

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

Authors:

Neslusan et al

Abstract:

Apart from thousands of `regular' exoplanet candidates, Kepler satellite has discovered a few stars exhibiting peculiar eclipse-like events. They are most probably caused by disintegrating bodies transiting in front of the star. However, the nature of the bodies and obscuration events, such as those observed in KIC8462852, remain mysterious. A swarm of comets or artificial alien mega-structures have been proposed as an explanation for the latter object.

We explore the possibility that such eclipses are caused by the dust clouds associated with massive parent bodies orbiting the host star.

We assumed a massive object and a simple model of the dust cloud surrounding the object. Then, we used the numerical integration to simulate the evolution of the cloud, its parent body, and resulting light-curves as they orbit and transit the star.

We 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 provides additional support for this hypothesis.

This model provides an alternative to the comet scenario. With such physical models at hand, at present, there is no need to invoke alien mega-structures for an explanation of these light-curves.

Did KIC 8462852 (Tabby's Star) Dim Because it Consumed an Exoplanet?

Secular Dimming of KIC 8462852 Following its Consumption of a Planet

Authors:

Metzger et al

Abstract:

The Kepler-field star KIC 8462852, an otherwise apparently ordinary F3 main-sequence star, showed several highly unusual dimming events of variable depth and duration. Adding to the mystery was the discovery that KIC 8462852 faded by 14% from 1890 to 1989, as well as by another 3% over the 4 year Kepler mission. Following an initial suggestion by Wright & Sigurdsson, we propose that the secular dimming behavior is the result of the inspiral of a planetary body or bodies into KIC 8462852, which took place ~10 to 1e4 years ago (depending on the planet mass). Gravitational energy released as the body inspirals into the outer layers of the star caused a temporary and unobserved brightening, from which the stellar flux is now returning to the quiescent state. The transient dimming events could then be due to obscuration by planetary debris from an earlier partial disruption of the same inspiraling bodies, or due to evaporation and out-gassing from a tidally detached moon system. Alternatively, the dimming events could arise from a large number of bodies comet- or planetesimal-mass bodies placed onto high eccentricity orbits by the same mechanism (e.g. Lidov-Kozai oscillations due to the outer M-dwarf companion) responsible for driving the more massive planets into KIC 8462852. The required high occurrence rate of KIC 8462852-like systems which have undergone recent major planet inspiral event(s) is the greatest challenge to the model, placing large lower limits on the mass of planetary systems surrounding F stars and/or requiring an unlikely probability to catch KIC 8462852 in its current state.

KIC 8462852's Dimming Revisited

A STATISTICAL ANALYSIS OF THE ACCURACY OF THE DIGITIZED MAGNITUDES OF PHOTOMETRIC PLATES ON THE TIMESCALE OF DECADES WITH AN APPLICATION TO THE CENTURY-LONG LIGHT CURVE OF KIC 8462852

Authors:

Hippke et al

Abstract:

We present a statistical analysis of the accuracy of the digitized magnitudes of photometric plates on the timescale of decades. In our examination of archival Johnson B photometry from the Harvard DASCH archive, we find a median rms scatter of light curves of the order of 0.15 mag over the range B ~ 9–17 for all calibrations. Slight underlying systematics (trends or flux discontinuities) are on a level of lesssim0.2 mag per century (1889–1990) for the majority of constant stars. These historic data can be unambiguously used for processes that happen on scales of magnitudes, and need to be carefully examined in cases approaching the noise floor. The characterization of these limits in photometric stability may guide future studies in their use of plate archives. We explain these limitations for the example case of KIC 8462852, which has been claimed to dim by 0.16 mag per century, and show that this trend cannot be considered as significant.

Tabby's Star (KIC 8462852) Anomaly NOT Likely to be due to Alien Activity

Sorry, E.T. lovers, but the results of a new study make it far less likely that KIC 8462852, popularly known as Tabby's star, is the home of industrious aliens who are gradually enclosing it in a vast shell called a Dyson sphere.

Public interest in the star, which sits about 1,480 light-years away in the constellation Cygnus, began last fall when Yale astronomer Tabetha ("Tabby") Boyajian and colleagues posted a paper on an astronomy preprint server reporting that "planet hunters" - a citizen science group formed to search data from the Kepler space telescope for evidence of exoplanets - had found unusual fluctuations in the light coming from the otherwise ordinary F-type star (slightly larger and hotter than the sun).

The most remarkable of these fluctuations consisted of dozens of uneven, unnatural-looking dips that appeared over a 100-day period indicating that a large number of irregularly shaped objects had passed across the face of the star and temporarily blocked some of the light coming from it.

Media interest went viral last October when a group of astronomers from Pennsylvania State University released a preprint that cited KIC 8462852's "bizarre light curve" as "consistent with" a swarm of alien-constructed megastructures.

The attention caused scientists at the SETI Institute to train its Alien Telescope Array on the star to see if they could detect any radio signals indicating the presence of an alien civilization. In November it reported finding "no such evidence" of signals with an artificial origin.

Then a study released in January by a Louisiana State University astronomer threw even more fuel on the fire of alien speculation by announcing that the brightness of Tabby's star had dimmed by 20 percent over the last century: a finding particularly difficult to explain by natural means but consistent with the idea that aliens were gradually converting the material in the star's planetary system into giant megastructures that have been absorbing increasing amounts of energy from the star for more than a century. That study has now been accepted for publication in the peer reviewed Astrophysical Journal.

However, a new study - also accepted for publication in the Astrophysical Journal - has taken a detailed look at the observations on which the LSU study was based and concluded there is no credible evidence that the brightness of the star been steadily changing over this period.

When the LSU study was posted on the physics preprint server ArXiv, it caught the attention of Vanderbilt doctoral student Michael Lund because it was based on data from a unique resource: Digital Access to a Sky Century @ Harvard. DASCH consists of more than 500,000 photographic glass plates taken by Harvard astronomers between 1885 and 1993, which the university is digitizing. Lund was concerned that the apparent 100-year dimming of Tabby's star might just be the result of observations having been made by a number of different telescopes and cameras that were used during the past century.

Lund convinced his advisor, Professor of Physics and Astronomy Keivan Stassun, and a frequent collaborator, Lehigh University astronomer Joshua Pepper, that the question was worth pursuing. After they began the study, the Vanderbilt/Lehigh group discovered that another team - German amateur astronomer Michael Hippke and NASA Postdoctoral Fellow Daniel Angerhausen - were conducting research along similar lines. So the two teams decided to collaborate on the analysis, which they wrote up and submitted to the Astrophysical Journal.

"Whenever you are doing archival research that combines information from a number of different sources, there are bound to be data precision limits that you must take into account," said Stassun. "In this case, we looked at variations in the brightness of a number of comparable stars in the DASCH database and found that many of them experienced a similar drop in intensity in the 1960's. That indicates the drops were caused by changes in the instrumentation not by changes in the stars' brightness."

Even if aliens are not involved, Tabby's star remains "the most mysterious star in the universe" as Boyajian described it in a TED talk she gave last February.

link.

KIC 8462852: Just a Bunch of Comets

KIC 8462852 - The Infrared Flux

Authors:

Marengo et al

Abstract:

We analyzed the warm Spitzer/IRAC data of KIC 8462852. We found no evidence of infrared excess at 3.6 micron and a small excess of 0.43 +/- 0.18 mJy at 4.5 micron, below the 3 sigma threshold necessary to claim a detection. The lack of strong infrared excess 2 years after the events responsible for the unusual light curve observed by Kepler, further disfavors the scenarios involving a catastrophic collision in a KIC 8462852 asteroid belt, a giant impact disrupting a planet in the system or a population of a dust-enshrouded planetesimals. The scenario invoking the fragmentation of a family of comets on a highly elliptical orbit is instead consistent with the lack of strong infrared excess found by our analysis.