Period and Light-Curve Changes in AP Leonis

Abstract

We present a detailed study of the period and light curve of the eclipsing binary AP Leo. We have investigated the period variation of the system in detail using a method proposed by Kalimeris et al. (1994a,b; AAA 061.117.039, AAA 062.117.142). The orbital period of the system exhibits a periodic variation which contains four components with different frequencies. Our result is very different from that of other investigators. We compared light curves obtained by other groups, and found that the light curve of the system has changed considerably. Based on an analysis, we investigated the physical mechanisms which may underlie the variations of the period and the light curve, and obtained some new results. We have concluded that the rapid light variation is probably caused by a pulsation of the common envelope, and that the mechanism causing the pulsation may be mass transfer between the two components, or its variation. In addition, we have found that the mass transfer and magnetic activity may simultaneously play an important role in the variations in the orbital period and the light curve of the system. The paper concludes with a discussion of the evolution of the system.