Period Analysis,Photometry, and Astrophysical Modelling of the Contact Eclipsing Binary BC Gruis

摘要

BC Gruis is a W UMa-type contact binary system of the W-subtype with the primary minimum 0.1 magnitude fainter than the secondary minimum. The period is currently 0.3073060 ± 0.0000001 day; it was 4 seconds longer between 1986 and 1991. There were small modulations of0.001-0.002 day in the Observed-Calculated diagram due to asymmetry in the light curves, most likely caused by star spots. An astrophysical model of the system was developed with a mass ratio of 1.2 determined from light curve analysis. The best fit to light curves in B, V,and I pass bands in 2014 was given by including two large cool star spots on the more massive, cooler component and 1 cool spot on the hotter star. In 2015, the asymmetry in the light curves was different and was modelled best with a hot spot on the more massive component at the neck joining the stars and 1 cool spot on the other component.