A photometric study of the W UMa-type system RZ Tauri

The present study deals with the problem of the orbital and physical parame ters' estimation of the W UMa type eclipsing binary RZ Tauri, based on the interpretation of new photometric U B V R observations. The Light curves ob tained at the Maidanak Observatory during 1989-91 show a slight asymmetry a round secondary minima and the small difference in the height of the succes sive maxima. They are analysed in the framework of the Roche computer model (Djurasevic, 1992a) by applying the inverse-problem method (Djurasevic, 1992b) based on Marquardt's (1963) algorithm. The analysis shows that RZ Tau system is in an overcontact configuration with q = m(2)/m(1) similar to 0.362 and i = 82 (o).8, generating total-annular eclipses. The best fitting is achieved with a bright active region on the secondary star, placed near the neck region between the components, with the temperature contrast between the spotted a rea and the surrounding photosphere being As = T-S/T-2 similar to 1.070. The spectral type of this system (F0 V) defines its behaviour as being betw een convective and radiative. Because of that we treated the gravity-darken ing coefficients as free parameters in the inverse problem. The obtained va lue (beta(1,2) similar to 0.215) is like to be appropriate for this case, s howing that the common envelope of RZ Tauri is partly convective. The basic parameters of the system and of the active region are estimated for all in dividual U,B, V and R light curves.