Analysis of the activity of the eclipsing binary WZ Cephei

Abstract

The present study deals with the problem of the orbital and physical parameters' estimation of the ac- tive eclipsing binary WZ Cep based on the interpretation of its photometric observations. The B and V light curves (Homann 1984), as well as the new ones obtained at the Maidanak Observatory in the B, V and R passbands dur- ing 1995, are analysed and discussed. These two groups of light curves show large dierences in their shape and in the depth of the primary minimum. Homann's light curves show big asymmetry, especially conspicuous in the dierent height of the successive maxima. The new obser- vations give light curves that are almost symmetric having signicantly shallower primary minimum. They are analysed in the framework of the Roche computer model (Djura sevi c 1992a) by applying the inverse problem method (Djura sevi c 1992b) based on Marquardt's (1963) algorithm. The model is generalised for the case of an overcontact conguration also. To ex- plain these light curves asymmetries and variations, the model involved spotted regions on the components. The analysis shows that WZ Cep system is in a slight overcon- tact conguration and that best tting is achieved with spotted regions on the primary star (SpF5), with the tem- perature contrast between the spotted area and the sur- rounding photosphere being As = Ts=T1 0:70. The mass ratio was estimated at the valueq =m2=m1 0:33, based on the light-curve analysis. The basic parameters of the system and of the spot- ted areas are estimated for all foregoing mentioned light curves. The obtained solutions show that there are no sig- nicant variations of the system's basic parameters es- timated by analysing these two groups of very dierent light curves. Consequently, the main variations in the light curves can be explained by the change of the position and the size of the spotted areas on the primary.