Characteristics of Long-Term Spot Activity on Several Late-Spectral-Type Stars

Abstract

Abstract We present our analysis of many-year photometry for several dozens of chromospherically active stars that exhibit solar-type activity (from our own observations as well as from data in the literature). Modeling of the distribution of cool photospheric spots, based on the zonal model, was performed, with several hundred models constructed. We find that, for most stars, their spots are located at intermediate and moderate latitudes and that the largest spotted areas can cover from 7 to 58% of the star’s surface. We demonstrate that a latitude drift of spots can be suspected for a number of stars, towards the equator as well as towards the pole; however, the rate of this drift is several times lower than for solar spots. For 15 stars, we detected the presence of activity cycles from 3 to 28 years long that reveal themselves in variations of the system’s brightness as well as in variations of the total spot coverage of the star. This paper is based on a talk presented at the memorial astrophysical workshop “Novelties in Understanding the Evolution of Binary Stars” dedicated to the 90th birthday of Prof. M.A. Svechnikov.