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Abstract:

We report on first results obtained in the framework of a larger study of oEA stars, i.e. Algol-type systems with oscillating components. We investigate an extended time series of high-resolution spectra of the oEA star RZ Cas taken in 2006. By comparing our model calculations with the observations, we try to determine the system and atmospheric parameters of RZ Cas. Starting values were obtained from uvby photometry and from an analysis of the mean out-of-eclipse spectra by means of the KOREL program. The fine tuning of the model was done using the modified SHELLSPEC code. With SHELLSPEC we determined an unusual large gravity darkening exponent of 0.5 for the secondary of RZ Cas. This value is far above the theoretical limit given by the Von Zeipel law but in good agreement with those obtained by Unno et al. in 1994. We attribute the large value of different large star spots on the front and back sides of the secondary with respect to the primary that exists in the result of mass-outflow from the donor to the gainer.