Spots and Activity of the M Dwarf KIC 1572802статья
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Дата последнего поиска статьи во внешних источниках: 8 февраля 2017 г.
Аннотация:The photometric variability of the M dwarf KIC 1572802 has been studied using the most complete observational data, obtained by the Kepler Space Telescope. Power spectra constructed from 59488 single brightness measurements over 1460 days (∼4 yr) show complex brightness variations. It is suggested that two peaks corresponding to the periods P =0 .37088d and P =0 .37100d are related to the presence of active regions at different latitudes on the differentially rotating star. Maps of the surface temperatureinhomogeneitiesareusedtoderivethepositionsoftheseactiveregions. Analysisofthesemaps suggests that a switch in the active latitudes occurred 590 days after the beginning of the observations. The variations of the positions of the active regions are also analyzed. These high-temporal-resolution observations revealed a short time-scale change in the active latitudes lasting about 7d, followed by a “flip–flop,” for the first time. The fraction of the surface of KIC 1572802 covered by spots is S ∼7%. Comparisonwithliterature data indicate that this S value forKIC 1572802 is substantially higher than the average spottedness of stars with temperatures of 3500–4500 K. This may indicate enhanced activity of KIC 1572802. The parameters of the differential rotation of the star are estimated; the inferred rotational velocity, Ω=0 .0056±0.0010,is substantially lower than the solar value, but comparable to Ω for the cool dwarfs HK Aqr and EY Dra. The value of the Rossby number Ro =0 .011 suggests that KIC 1572802 is in the saturation region of the diagram of Ro vs. X-ray luminosity. If the Ro value for KIC 1572802 is this low,this impliesthat its magnetic fieldis of the orderof tens oreven hundreds of Gauss.