Hot Binaries: Observational Results

                              William I. Hartkopf
                                      USNO

Hot stars have long been the target of duplicity surveys by various astrometric and spectroscopic 
methods. Interferometric techniques (speckle, long-baseline, AO, HST/FGS, etc.) bridge the 
traditional separation/period gap between the visual and spectroscopic regimes, and O stars, 
Wolf-Rayets, and Be stars have all been studied by these techniques over the past few decades. A 
large 1994 speckle survey of Galactic O stars was recently followed up and expanded upon at the 
KPNO and CTIO 4-m telescopes. Some interferometrically-discovered hot binaries have now been 
observed a sufficient length of time to show obvious orbital motion.

The results of nearly four decades of interferometric study of hot stars will be summarized, 
encompassing data obtained by various high-resolution techniques. Duplicity rates for various 
classes of hot stars will be discussed, as well as more detailed findings for some individual pairs 
of interest. Finally, brief mention will be made of a project now underway to improve the sample of 
known runaway stars, this sample to become a possible SIM target list for distance determination.