1999A&A...343..894D

The present study deals with the problem of the orbital and physical parameters' 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 obtained at the Maidanak Observatory during 1989-91 show a slight asymmetry around secondary minima and the small difference in the height of the successive maxima. They are analysed in the framework of the Roche computer model (Djurasevic, 1992Ap&SS.196..241D) by applying the inverse-problem method (Djurasevic, 1992Ap&SS.197...17D) based on Marquardt's (1963, J. Soc. Ind. Appl. Math. 11 No. 2, 431) algorithm. The analysis shows that RZ Tau system is in an overcontact configuration with q=m₂/m₁∼0.362 and i=82.8°, 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 area and the surrounding photosphere being A_S=T_S/T₂∼1.070. The spectral type of this system (F0 V) defines its behaviour as being between convective and radiative. Because of that we treated the gravity-darkening coefficients as free parameters in the inverse problem. The obtained value (β_1,2∼0.215) is like to be appropriate for this case, showing 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 individual U, B, V and R light curves.