Long-term starspot activity of three short-period RS CVn stars: BH Vir, WY Cnc and CG Cyg

Abstract

We present starspot analyses of CG Cyg, BH Vir and WY Cnc on the basis of our new photometric observations as well as published photometric data spanning almost 40 years. The spotted regions were concentrated at low latitudes up to 32°, the spots covered up to 29% of the stellar surface and all three stars show non-axisymmetric spot distributions (active longitude structures separated by approximately half the orbital period). We found that the variations in the brightness and spottedness of CG Cyg are probably cyclic with a period of about 20 years. We detected a large flare on WY Cnc (1.02×1035 erg in the B band) and analysed the WY Cnc spot activity before and during the flare.