Period Changes of Two W UMa–Type Contact Binaries: RW Comae Berenices and CC Comae Berenices

Abstract

ABSTRACTFrom the present times of minimum light and those collected from the literature, changes in the orbital period of the two W UMa–type contact binaries RW Com and CC Com are analyzed. The results reveal that the period changes of these two systems show the same natures, with a short‐term oscillation superposed on the secular decrease. For RW Com, its period shows a secular decrease at a rate of dP/dt = 0.43 × 10-7 days yr−1. An oscillation with a periodicity of 13.7 yr and an amplitude of ΔP = 5.4 × 10-7 days is superposed on the secular decrease. For CC Com, its period shows a secular decrease at a rate of dP/dt = 0.40 × 10-7 days yr−1. An oscillation with a periodicity of 16.1 yr and an amplitude of ΔP = 2.8 × 10-7 days is superposed on the secular decrease. The period secular decreases of the two systems may be explained by a mass‐transfer rate of dm/dt = 0.29 × 10-7 M⊙ yr-1 for RW Com and dm/dt = 0.52 × 10-7 M⊙ yr-1 for CC Com. The period short‐term oscillations of the two systems may be explained by the magnetic activity cycle model given by Applegate, and the parameters for the magnetic activity cycle model are presented.