A PULSATING FLARE STAR IN THE NEW PLANETARY SYSTEM: KOI-258

Abstract

We present findings about the nature of KOI-258. Its temperature was found to be 6500 ± 200 K from its spectrum, which also indicates that the target is a single main sequence star despite the existence of a radial velocity variation with a small amplitude. Ca II H, K lines indicate the existence of magnetic activity, though there is no remarkable excess or variation in the Hα line. We found 51 flares with a frequency of 0.00186 h−1, whose plateau value is 0.659 s. Apart from the flares, we found 420 frequencies due to solar-like oscillations at out-of-eclipses. Removing these 420 frequencies, we demonstrated three different transits caused by three exo-planets. Their radii were found to be 2.33 R_⊕ for the first planet, 0.53 R_⊕ for the second one, and 1.15 R_⊕ for the third planet. Consequently, KOI-258 is an oscillating, single, main sequence star, with in a planetary system and remarkable flare activity.