CCD photometry, Roche modelling and period analysis of the W UMa eclipsing binary star system AR CrB

Abstract

AR CrB (GSC 2040-1361) is a W UMa-type binary system (P = 0.397351 d) which has been poorly studied since first detected over 17 yr ago; only a single unfiltered light curve (LC) has been published. Photometric data collected in three bandpasses (B, V, and R_c) at UnderOak Observatory produced four new times-of-minimum for AR CrB. These along with other published eclipse timings (ET) were used to update the linear ephemeris and further analyse potential changes in orbital periodicity by examining the ET differences (ETD). Synthetic LC fitting by Roche modelling was accomplished using the WILSON-DEVINNEY code. Recent radial velocity data has now allowed us to report the absolute and geometric parameters for this partially eclipsing binary system. A spotted solution was necessary to achieve the best Roche model fits for the AR CrB LCs collected in 2012. Although no obvious change in orbital period has occurred when comparing the observed versus calculated timings at minimum light, the paucity of LC data available since 1999 limits its predictive value; minima need to be collected over a much longer time-scale to determine whether there are real changes in the periodicity of this W-subtype W UMa system.