R. Chini, A. Barr, L. S. Buda, T. Dembsky, H. Drass, A. Nasseri, V. H. Hoffmeister, K. Fuhrmann
We report about an ongoing photometric and spectroscopic monitoring survey of about 250 O- and 540 B-type stars in the southern Milky Way with the aim to determine the fraction of close binary systems as a function of mass and to determine the physical parameters of the individual components in the multiple systems. Preliminary results suggest that the multiplicity rate drops from 80% for the highest masses to 20% for stars of 3 solar masses. Our analysis indicates that the binary systems often contain close pairs with components of similar mass. This coincidence cannot originate from a random tidal capture in a dense cluster but is likely due to a particular formation process for high-mass stars. The large percentage of multiple systems requires a new photometric calibration for the absolute magnitudes of O-type stars.
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http://arxiv.org/abs/1306.1811
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