Activity of the Young Star EPIC 204376071 from the Upper SCO Association

Abstract

Based on observations from the K2 mission of the Kepler Space Telescope a study is made of the activity of EPIC 204376071, a young object in the Upper SCO association with an age of 11±3 million years whose light curve has a single darkening lasting one day with a depth of about 80%. EPIC 204376071 is a low-mass M-dwarf with a mass of 0.16 M_⨀. Based on observations from the C15 campaign of the K2 mission we refined the rotation period and the amplitude of the variability of the star’s brightness, and also estimated the absolute magnitude of the spottedness parameter A by the standard method. The magnitude of the star’s rotation period, P, equals 1.6270 ± 0.030 days. The area of the spots on the surface of EPIC 204376071 exceeds the maximum spot area on the sun and is on the order of 7900 msh. The results of a recovery of the temperature inhomogeneities on the surface of EPIC 204376071 are presented. Two cold regions separated in longitude by roughly 150° can be distinguished on the constructed chart. For estimating the properties of the flare activity of EPIC 204376071 one of the most reliable flares with a brightness amplitude of about 4% was examined. The measured relative energy RE of the flare was 212 s. The calculated energy E_fl of the flare turned out to be equal to 1.1·1034 erg (logE_fl = 34.05). The probable coronal mass ejection corresponding to it may reach 4.1·10²⁰ g. Published data on the possible nature of the single occultation of diurnal duration with a depth of about 80% on the light curve of EPIC 204376071 are examined.