Detection of a repeated transit signature in the light curve of the enigma star KIC 8462852: a 928-day period?

TL;DR

This paper reports the discovery of two similar dimming events in KIC 8462852 separated by 928 days, suggesting a possible periodic transit of a large object or system, with implications for understanding its peculiar light curve.

Contribution

It identifies a potential 928-day periodicity in the star's dimming events, proposing a giant ring system or a string of exocomets as the cause, which is a novel interpretation of the star's behavior.

Findings

Two similar dimming events separated by 928 days.

The events are consistent with a giant ring system or multiple exocomets.

Predicted next transit between October 3-8, 2019.

Abstract

As revealed by its peculiar Kepler light curve, the enigmatic star KIC 8462852 undergoes short and deep flux dimmings at a priori unrelated epochs. It presents nonetheless all other characteristics of a quiet 1 Gyr old F3V star. These dimmings resemble the absorption features expected for the transit of dust cometary tails. The exocomet scenario is therefore most commonly advocated. We reanalyzed the Kepler data and extracted a new high-quality light curve to allow for the search of shallow signature of single or a few exocomets. We discovered that among the 22 flux dimming events that we identified, two events present a striking similarity. These events occurred 928.25 days apart, lasted for 4.4 days with a drop of the star brightness by 1000 ppm. We show that the light curve of these events is well explained by the occultation of the star by a giant ring system, or the transit of a string of half a dozen of exocomets with a typical dust production rate of 10$^5$-10$^6$ kg/s. Assuming that these two similar events are related to the transit of the same object, we derive a period of 928.25 days. The following transit was expected in March 2017 but bad weather prohibited us to detect it from ground-based spectroscopy. We predict that the next event will occur from the 3rd to the 8th of October 2019.