  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.
