2014MNRAS.442.3769K

An investigation of the G-type stellar population with Kepler (as done by Maehara et al.) shows that less than 1 percent of those stars show superflares. Due to the large pixel scale of Kepler (~4 arcsec/px), it is still not clear whether the detected superflares really occur on the G-type stars. Knowing the origin of such large brightenings is important to study their frequency statistics, which are uncertain due to the low number of sun-like stars (Teff = 5600-6000K and Prot > 10d) which are currently considered to exhibit superflares. We present a complete Kepler data analysis of the sun-like stars KIC10524994 and KIC07133671 (the only two stars within this subsample of solar twins with flare energies larger than 10³⁵erg; Maehara et al.), regarding superflare properties and a study about their origin. We could detect four new superflares within the epoch Maehara et al. investigated and found 14 superflares in the remaining light curve for KIC10524994. Astrometric Kepler data of KIC07133671 show that the photocentre is shifted by 0.006 px or 25 mas during the one detected flare. Hence, the flare probably originated from another star directed towards the north-east. This lowers the superflare rate of sun-like stars (and hence the Sun) for E > 10³⁵erg, since this additional star is probably not solar-like.