Automatic Parametrization of Gaia Astrometrically Unresolved Binary Stars

We have simulated 1X photometry of spectroscopic binary stars as they will be observed by Gaia to test how well the stellar physical parameters (Teff1 , Teff2 , log g1, log g2 and [Fe/H] in addition to extinction AV ) can be determined from such unresolved objects. Both single shot (SS) and end-of-mission (EM) data was analysed and the results compared to those for single stars. We find that the parametrization performance is a strong function of the logarithmic luminosity ratio log(Lr) and also depends on the underlying grid of stellar parameter combinations. The primary star's Teff1 and log g1 are parametrized at a similar precision as for a single star. The same applies to [Fe/H] and AV , the two systemic parameters.