New Period Investigation of Near Contact Binary BF Virginis

Abstract

Abstract The near contact binary BF Virginis was monitored by us from 2007 to 2011 with the 60-cm telescope of Yunnan Observatory. Eight new observed times of light minimum were derived. All of the available eclipse times, spanning more than 100 yr, were analyzed. It is found that there exists a cyclic variation with a semi-amplitude of 0.034 d and a period of 63.3 yr, superposed by an upward parabolic variation. The upward parabolic change can be explained as a continuous period increase due to mass transfer from the secondary to the primary component of BF Vir, which supports the secondary filling near contact configuration. The period oscillation can be explained either by the light-time effect due to the presence of a third body or by magnetic activity. If it is caused by the light-time effect, the minimum mass and the corresponding orbital radius of the additional body should be $ m_{3}$$ =$ 0.93 $ M_{\odot}$ and $ a_{3}$$ =$ 19.4 AU, respectively. On the other hand, the period oscillation may be explained as a consequence of magnetic cycles in its secondary component. In this case, the required variation of the quadrupole moment is calculated to be $ \Delta{Q}$$ =$ 2.1 $ \times$ 10$ ^{50}$ g cm$ ^2$ .