An interpretation of light curves of SV Camelopardalis by the inverse-problem method

Abstract

The paper is devoted to the problem of the determination of the orbital and physical parameters of the active eclipsing binary SV Cam on the basis of the in- terpretation of photometric observations made by Patk os (1982) during the period 1973-1981. The problem is solved in two stages: by obtaining a synthetic light curve in the case when the parameters of the corresponding Roche model (Djura sevi c 1992a) are given a priori (direct prob- lem), and by determining the parameters of the model for which the best t between the synthetic light curve and the observations is achieved (inverse problem) (Djura sevi c 1992b). A total of 18 light curves are analysed in the framework of the Roche model, involving one and two spotted regions on the primary component of the system (Sp G3 V), for the temperature contrast between the spot- ted area and the surrounding photosphere As = Ts=T1 = 0:65. The basic parameters of the system and of the spot- ted areas are estimated. Throughout the whole set of the analysed light curves, a double spot model ts the observa- tions satisfactorily. A single spot model yields a poorer t, where the basic system parameters obtained by analysing the individual light curves show stronger variations about a mean value. That indicates that the single spot model cannot successfully reproduce the SV Cam light curve changes during the analysed period. According to the obtained results the spotted areas are formed at high latitudes and cover a signicant part of the stellar surface. No clear cyclicity of the system's activity is noted from the analysed observations. There are some indications that spotted areas at high latitudes (above 70 o ) correspond to an enhanced activity. Since the system's period is short (P =0 : d 59), the presence of spot- ted regions at high latitudes can be explained by the dy- namo mechanism for rapid rotators (Schussler & Solanski 1992). During the analysed period the spotted areas tend to fall into a specially active longitude sectors at high lat- itudes, near stellar polar regions. Due to a selection eect Send oprint requests to :G. Djura sevi c it is possible that a more extensive observational material would correct this result to some extent. The light curve analysis allowed an estimation of the system parameters and of the active spotted regions.