Subdwarf B–Stars and Binarity

Spectroscopic and photometric data give evidence for a large fraction of binary stars among hot subdwarfs. Since our work aims at determining atmospheric parameters and distances of sdB and sdOB stars, we have to take special care of this aspect. We try to deconvolve the photometric data and derive colours for the subdwarf component of the binary. The impact of binarity in hot subdwarfs to their evolutionary history is briefly discussed.