A comprehensive photometric study of the eclipsing binary EP Aurigae

We present new observations for the eclipsing binary EP Aurigae, which were performed by using three small telescopes in China from 2003 December to 2014 January. With the updated 2003 version of the Wilson-Devinney code, the photometric elements were deduced from three sets of light curves. Based on all available eclipsing times, the orbital period changes were investigated. It is discovered that the (0 C) curve may show an existence of light-time effect due to an unseen third body, which was weakly identified by the photometric solution. The modulated period and amplitude of the cyclic variation are P-3 = 71.2(+/- 8.0) yr and A = 0.0101(+/- 0.0008) day, respectively. In the co-planar orbit with the binary system, the mass of the third body is M-3 = 0.18(+/- 0.02) M-circle dot. The photometric results imply that EP Aur is an Algol-type binary with a mass ratio of q = 0.831(+/- 0.004). Its primary component almost fills its Roche lobe. Therefore, EP Aur may consist of a normal main-sequence star and a cool Roche-lobe filling subgiant, which may be undergoing rapid mass transfer. (C) 2014 Elsevier B.V. All rights reserved.