Be stars in binaries.

The known companions to 80 Be stars and 355 B stars listed in the Bright Star Catalogue in the range B1-B7 III-V and north of delta = -30 deg are considered. The known near-absence of Be binaries with periods less than 1/10 yr is confirmed. For longer periods up to the limit of 10,000 AU of this survey, the Be and B stars do not differ in binary frequencies. This result implies that during pre-main-sequence contraction, the tidal braking in binaries wider than 0.5 AU was inadequate to prevent the formation of stars with nearly the break-up rotational velocities. The fraction of Be and B stars that have companions is higher in clusters and associations (38 percent) than among field stars (25 percent), confirming that escapees from clusters tend to be single stars. There is some evidence that the companions of Be stars that occur in the same luminosity range tend also to be Be stars; that result was expected because in visual binaries there is a known tendency for rapidly rotating primaries to have rapidly rotating secondaries.