Secular Dimming of KIC 8462852 Following its Consumption of a Planet

TL;DR

This paper proposes that the unusual dimming of KIC 8462852 is caused by planetary inspiral events, with energy release and debris obscuration explaining the star's long-term and transient dimming behaviors.

Contribution

It introduces a novel model linking the star's secular dimming and transient events to recent planetary inspiral and debris, offering a new explanation for its unusual light curve.

Findings

Secular dimming from planetary inspiral over 10 to 10,000 years.

Transient dimming caused by debris from disrupted planets or moons.

High occurrence rate of such systems challenges the model's probability.

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.