DETECTING RED STELLAR COMPANIONS TO HOT SUBDWARFS WITH CCD IMAGING

A search for red stellar companions to hot subdwarfs, using BRI and Z filter CCD imaging, is presented. 5, possibly 6, companions to 20 sdB and sdO stars have been detected-only one of which has been previously reported. For the sdB PG0822+645 the found companion corresponds to a wide binary system, which is also the case for the sdO Mrk509C. These systems should therefore be common proper motion pairs. The details o f a search for a previously proposed companion to Feige 34 are given - there is no evidence for a resolvable companion, and the analysis of the photometry of the companion to the sdO Mrk509C is given. Distance and gravity for the sdO are predicted, for various assumptions.