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

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 3 rd to the 8 th of October 2019.

Extrasolar enigmas: from disintegrating exoplanets to exoasteroids

“…A similar idea was presented earlier in [131]. The authors identified two strikingly similar events in the Kepler light curve which are approximately 0.1% deep and occurred at D216 and D1144.…”

Transiting exocomets detected in broadband light by TESS in the β Pictoris system

“…This work recovered the events discovered by Rappaport et al (2018), found one more around HD 182952, and argued that the host stars are likely young (∼100Myr old). For completeness, we note that the deep and irregular dimming events seen towards KIC 8462852 have also been interpreted as having a cometary origin (Boyajian et al 2016;Wyatt et al 2018;Kiefer et al 2017), although the shape and depth of these events are very different to those discovered by Rappaport et al (2018) and Kennedy (2018).…”

The First Post-Kepler Brightness Dips of KIC 8462852

“…KIC 8462852's variability manifests itself as asymmetric drops in brightness of up to 22%, many of which last several days (the "dips"). There is little or no sign of periodicity in the four years of Kepler observations (but see Kiefer et al 2017). Additionally, the duty cycle of the dips is low, occurring for less than 5% of the four-year period Kepler observed it.…”