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

Abstract

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 interpretation of photometric observations made by Patkós (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 (Djurašević 1992a) are given a priori (direct problem), and by determining the parameters of the model for which the best fit between the synthetic light curve and the observations is achieved (inverse problem) (Djurašević 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 spotted area and the surrounding photosphere A s = T s /T 1 = 0.65. The basic parameters of the system and of the spotted areas are estimated. Throughout the whole set of the analysed light curves, a double spot model fits the observations satisfactorily. A single spot model yields a poorer fit, 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 significant 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 spotted regions at high latitudes can be explained by the dynamo mechanism for rapid rotators (Schüssler & Solanski 1992). During the analysed period the spotted areas tend to fall into a specially active longitude sectors at high latitudes, near stellar polar regions. Due to a selection effect Send offprint requests to: G. Djurašević 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.

Spectroscopic observations of the short-period, RS CVn-type star SV Cam

“…It should be noted that the values of r 1 and r 2 determined by different authors lie in the ranges 0.32-0.4 and 0.19-0.25 (Budding & Zeilik 1987;Zeilik et al 1988;Patkos & Hempelmann 1994;Djurasevic 1998;Heckert et al 1998). The radii of the components of SV Cam corresponding to their masses calculated from the mass-radius relation for MS stars are R 1 = 1.32 R and R 2 = 0.91 R for the primary and secondary, respectively.…”

A spectroscopic study of the eclipsing binaries SV Camelopardalis and XY Ursae Majoris

“…Djurasević (1998) claimed that a double spot model fits the observations better than the previously used single spot model.…”

“…Since discovered as a variable star by Guthnick (1929), SV Cam has been observed by Wood (1946), Van Woerden (1957), Hilditch et al (1979) and Patkos (1982). The light curves have been analysed by Zeilik et al (1988), Budding (1977), Budding & Zeilik (1987) and Djurasević (1998), using spot modelling techniques. According to these authors, a single active darkspotted region covers a significant part of the stellar surface at high latitudes and is responsible for the migration waves which tend to fall into two longitude sectors, 45…”

The eclipsing active star SV Camelopardalis

“…Correspondence to: patkos@konkoly.hu modeled by many investigators , Patkós & Hempelmann 1994, Djurasevic 1998. In this paper we present new observations from the years 1993-1994 which were not published elsewhere 1 .…”

“…SV Camelopardalis has got a lot of light curve solutions (e. g. Zboril & Djurasevic 2003;Frigo et al 2002;Albayrak et al 2001;Kjurkchieva et al 2000;Djurasevic 1998;Hempelmann et al 1997;Heckert 1995;Patkós & Hempelmann 1994;Sarma et al 1991;Budding & Zeilik 1987). Hereafter we give a new light curve solution based on new measurements of the spectroscopic mass ratio.…”