A SURVEY FOR H-ALPHA EMISSION IN MASSIVE BINARIES - THE SEARCH FOR COLLIDING WIND CANDIDATES

I report the results of the first all-sky survey of H alpha emission i n the spectra of O-type binaries. The survey includes 26 systems, of w hich 10 have emission that extends clearly above the continuum. This i s the first report of emission for four of these. An additional three systems show small distortions in the H alpha profile that may result from weak emission. I compare the distribution of emission systems in H-R diagrams for both binary and single stars, using a survey of singl e O-type stars done by Conti (1974). Emission in main-sequence systems is extremely rare and is completely absent in my sample of binary sta rs. Among binary stars, 78% of the systems containing giants show some emission, while no single giants in Conti's sample do. In the case of supergiants, 78% of single stars show emission, while all supergiant binaries show strong emission. H alpha emission may come from a variet y sources, but the fact that binaries have a higher incidence and stre ngth of emission in post-main-sequence stages may indicate that wind i nteractions are a common source of emission in massive binaries. To as certain whether or not colliding winds have been observed, it will be necessary to study the H alpha line profile throughout several orbits of each candidate colliding wind system and look for recurring orbital -phase-related variations. Such a study is underway.