2002A&A...395..587Z

We present photometric observations of the eclipsing binary GR Tau made in 1985, 1993, 1998, 2000 and 2001. New times of minima and ephemerides are given. Based on a statistical analysis of the times of minima obtained by photoelectric and CCD photometry, the orbital period of the system is found to be decreasing with a rate of ΔP/P=3.27x10^–10 during the past decades. An assumed hot spot on the trailing hemisphere of the secondary enables us to reconstruct the peculiar asymmetry of the distorted light curves. The photometric solution with the Wilson-Devinney code reveals that GR Tau is a near-contact detached system with the two components almost filling their respective critical Roche lobes. The photometric mass ratio turns out to be q=0.22, and the masses and radii are derived for the components as M₁=1.42±0.18M_☉, M₂=0.31±0.04M_☉, R₁=1.47±0.19R_☉ and R₂=0.70±0.09R_☉. The authors discuss the possible evolutionary status of the component stars and the probable nature of the assumed hot spot.