Spectroscopy of 341 bright A- and B-type stars

The companion mass-ratio distribution is a unique probe into the conditions of the collapsing cloud core and circumstellar disk(s) of the binary fragments. Inside a~1000AU the disks from the two forming stars can interact, and additionally companions can form directly through disk fragmentation.

We should, therefore, expect the mass-ratio distribution of close companions (a<~100AU) to differ from that of wide companions. This prediction is difficult to test using traditional methods, in particular, with intermediate-mass primary stars, for a variety of observational reasons. We present the results of a survey searching for companions to A- and B-type stars using the direct spectral detection method, which is sensitive to late-type companions within ~1'' of the primary and which has no inner working angle.