Metallicity-dependent effective temperature determination for eclipsing binaries from synthetic UVBY Strömgren photometry

Str ¨ omgren synthetic photometry from an empiri- cally calibrated grid of stellar atmosphere models has been used to derive the effective temperature of each component of double lined spectroscopic (SB2) eclipsing binaries. For this purpose, we have selected a sub-sample of 20 SB2s for which (b y), m1, and c1 individual indices are available. This new determi- nation of effective temperature has been performed in a homo- geneous way for all these stars. As the effective temperature determination is related to the assumed metallicity, we explore simultaneous solutions in the (Te ,(Fe=H))-plane and present our results as confidence regions computed to match the ob- served values of surface gravity, (b y), m1, and c1, taking into account interstellar reddening. These confidence regions show that previous estimates of Te are often too optimistic, and that (Fe=H) should not be neglected in such determinations. Com- parisons with Ribas et al. (1998) using Hipparcos parallaxes are also presented for 8 binaries of our working sample, showing good agreement with the most reliable parallaxes. This point gives a significant weight to the validity of the BaSeL models for synthetic photometry applications.