Multiwavelength Observations of Gamma-ray Binaries

The recent launch of the Fermi Gamma-ray Space Telescope has renewed interest in the rare class of high mass X-ray binaries that also have MeV-TeV gamma-ray emission. These systems consist of a hot, mass donor star and an unknown compact companion (either a neutron star or black hole). Two of the best known gamma-ray binaries are LS I +61 303 and LS 5039. I will present recent observations of LS I +61 303 that reveal a tidal mass stream that interacts with the compact companion for a fraction of the binary orbital period. A correlated burst in radio, X-ray, and gamma-ray emission is observed when the stream reaches the compact companion. Radio and optical observations of LS 5039 do not show evidence for a similar stream in that system, so I will discuss alternate ways to produce the very high energy emission.