A Period Study of the Near-Contact Binary IR Cassiopeiae

Abstract

The near-contact binary IR Cas was observed in 2003 October. Two new observed times of the primary minimum were derived. All of the available eclipse times, including the new ones, spanning 90 years were analyzed. It was shown that the period change of the system is very complex. A period oscillation with a period of 53.24 years and an amplitude of about 0.0133 days were found, while it undergoes a secular decrease at a rate of $dP/dt =-1.18 \times 10^{-7} (\pm0.09) \,\mathrm{d} \,\mathrm{yr}^{-1}$. The mechanisms that could explain the period changes and the evolutionary state of the system are discussed.