The eccentric Koza–Lidov mechanism as the cause of exocomet transits of KIC 8462852

Abstract

ABSTRACT KIC 8462852 is a star in the Kepler field that exhibits almost unique behaviour. The deep, irregular, and aperiodic dips in its light curve have been interpreted as the breakup of a large exocomet on a highly eccentric orbit whose post-disruption material obscures the star. It is hypothesized that a nearby M-dwarf, recently confirmed to be bound to the system, could be exciting planetesimals in a source belt to high eccentricities if its orbit is highly misaligned with the belt: an effect known as the ‘Eccentric Kozai–Lidov Mechanism’. To quantify how often this effect is expected to occur, this paper presents a Monte Carlo model of wide binary stars with embedded, misaligned planetesimal belts. These belts collisionally erode over time until they are excited to high eccentricities on secular time-scales by a companion star if its orbit is sufficiently misaligned. The large planetesimals then produce an observable dimming signature in the light curve for a set period of time which may or may not overlap with similar events. The model finds that, for dimming events that persist for 100 yr, the most likely companion stars are located at 102−104 au, the most likely belts are at 102−103 au and the system age is most likely to be 102−103 Myr. However, the probability of observing one or more stars exhibiting this phenomenon in the Kepler field is 1.3 × 10−3, such that it is unlikely this mechanism is driving the observations of KIC 8462852.