An X-Ray Survey of Colliding Wind Binaries

We have compiled a list of 35 O + O binaries and 86 Wolf-Rayet (WR) binaries in the Milky Way and Magellanic clouds detected with the Chandra, XMM-Newton, and ROSAT satellites to probe the connection between their X-ray properties and their system characteristics. Of the WR binaries with published model parameters, all have log L-X > 32, kT > 1 keV and log L-X/L-bol > -7. The most X-ray luminous WR binaries are typically very long period systems. The WR binaries show a nearly four-order of magnitude spread in X-ray luminosity, even among among systems with very similar WR primaries. Among the O + O binaries, short-period systems have soft X-ray spectra and longer period systems show harder X-ray spectra again with a large spread in L-X/L-bol.