Dynamo activity of the K dwarf KOI-883 from transit photometry mapping

ABSTRACT The Kepler mission target star KOI-883 is notable in being a low-mass K2V dwarf with moderately fast 8.99-d rotation and hosting a single transiting hot Jupiter in a 2.69-d orbit. This combination thus presents a particular opportunity to study star-spot activity by using the many deep planetary transits apparent in the light curve to map the stellar surface. The data have been analysed using spot modelling and temporal mapping methods we have used for other Kepler host stars, and a search for flares was conducted. Our results indicate a low-latitude region of the photosphere marked by distinct areas of individual or grouped star-spots with moderately high solar-type differential rotation of 0.102 ± 0.011 rad d−1, but with just two major flares observed across 400 d. These results imply a rotational shear significantly greater than that of our slower rotating Sun. The observed flares are more energetic than typical solar flares, but similar to those of other magnetically active cool dwarfs.