Publication Date:
2019-07-13
Description:
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(sub 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 approximately equal to 0.1 percent 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 artifacts as sources of the signals. We fit the transits with a simple dust-tail model, and find that a transverse comet speed of approximately 35-50 km s(exp -1) and a minimum amount of dust present in the tail of approx. 10(exp 16) g are required to explain the larger transits. For a dust replenishment time of approx. 10 days, and a comet lifetime of only approx. 300 days, this implies a total cometary mass of approx. greater than 3 x 10(exp17) 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.
Keywords:
Lunar and Planetary Science and Exploration
Type:
ARC-E-DAA-TN48399
,
Monthly Notices of the Royal Astronomical Society (ISSN 0035-8711) (e-ISSN 1365-2966); 474; 2; 1453-1468
Format:
application/pdf
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