Activity of the Red Dwarf FR Cnc from Observations with a Robotic IRT-20 Telescope at the Zvenigorod Observatory of INASAN

Abstract

We present the results of our new photometric observations of the chromospherically active star FR Cnc performed with a robotic telescope at the Zvenigorod Observatory of INASAN in March 2019. The observations were carried out from March 2 to 13, 2019, in the period of time that coincided most closely in time interval with the observations of this star with the Astrosat space telescope. A total of 450 magnitude estimates were obtained in each of the B, V, and R photometric bands over 12 days (from HJD 2458545.2 to HJD 2458556.5). Based on the V-band photometric variability of the star, we have constructed a map of surface temperature inhomogeneities. According to our estimate, the spot area on the surface of the star was ~12% of its total surface area in early 2019. On March 3, 2019, a flare on FR Cnc was detected during our observations at a time corresponding to HJD = 2458554.25891447 or rotation phase 0.8. The data for the flare suggest a rapid brightening of the star by 0.19m in the B band and by 0.09m in the V band; the flare lasted for about 60 min. The energy radiated in the flare was ITEB = 2.17 × 1033 erg and Ey = 1.40 × 1033 erg in the B and V bands, respectively.