Likely transiting exocomets detected by Kepler

Abstract

We present the first good evidence for exocomet transits of a host star in continuum light in data from the Kepler mission. The Kepler star in question, KIC 3542116, is of spectral type F2V and is quite bright at K p = 10. The transits have a distinct asymmetric shape with a steeper ingress and slower egress that can be ascribed to objects with a trailing dust tail passing over the stellar disk. There are three deeper transits with depths of 0.1% that last for about a day, and three that are several times more shallow and of shorter duration. The transits were found via an exhaustive visual search of the entire Kepler photometric data set, which we describe in some detail. We review the methods we use to validate the Kepler data showing the comet transits, and rule out instrumental artefacts as sources of the signals. We fit the transits with a simple dust-tail model, and find that a transverse comet speed of ∼35-50 km s −1 and a minimum amount of dust present in the tail of ∼ 10 16 g are required to explain the larger transits. For a dust replenishment time of ∼10 days, and a comet lifetime of only ∼300 days, this implies a total cometary mass of 3 × 10 17 g, or about the mass of Halley's comet. We also discuss the number of comets and orbital geometry that would be necessary to explain the six transits detected over the four years of Kepler prime-field observations. Finally, we also report the discovery of a single comet-shaped transit in KIC 11084727 with very similar transit and host-star properties.

A 9-h CV with one outburst in 4 yr of Kepler data

“…J.) visually inspected all ∼200,000 of the Kepler lightcurves (see, e.g., Rappaport et al 2018). One unusual object that was found was KIC 5608384, a red star previously cataloged as a variable star (V0754 Lyr, Kryachko et al 2010; ASASSN-V J191223.18+404952.8, Shappee et al 2014, Kochanek et al 2017, which exhibits one CV-like outburst during the fouryears of observation.…”

Planetary Candidates Observed by Kepler. VIII. A Fully Automated Catalog with Measured Completeness and Reliability Based on Data Release 25

“…Systems with only two transits (which would not be made into KOIs) or systems with single transits from several orbiting bodies would not be identified in this way. For example, KIC3542116 was identified by Rappaport et al (2017) as a star with possible exocomets, and it is an scrTCE dispositioned as an FP. We expect the effect of not removing these unusual events to be negligible on our reliability measurements relative to other systematic differences between the obsTCEs and the scrTCEs.…”

Planetesimals around stars with TESS (PAST) – I. Transient dimming of a binary solar analogue at the end of the planet accretion era

“…Low-amplitude ( 1%) quasi-periodic dipping with Keplerian regularity but varying amplitude and shape has been explained by dust clouds emanating from "evaporating" ultra-short period planets which by themselves are too small to produce a detectable transit signal (Rappaport et al 2012;Sanchis-Ojeda et al 2015). Lowamplitude dips with shapes consistent with transiting "exocomets" have been identified in the light curves of several main sequence stars, none of which have detectable infrared excess indicative of disks (Rappaport et al 2018;Ansdell et al 2019;Zieba et al 2019); the transiting objects could be larger analogs to the Sun-grazing comets discovered by the SOHO satellite (Battams & Knight 2017;Jones et al 2018). The anomalous star KIC 8462852 (Boyajian et al 2016) may be the extreme member of a population of such stars (Wyatt et al 2018).…”