HIPPARCOS RESULTS ON MASSIVE X-RAY BINARIES

We present results on parallaxes, magnitudes and proper motions for 17 optically identified massive X-ray binaries (MXRB) which were observe d during the Hipparcos astrometry mission. This sample includes the so urces detected in the medium-energy range (2-10 keV) having optical co unterparts brighter than V=12. We compare the Hipparcos results with g round-based optical data and derive probable values for absolute magni tudes and peculiar tangential velocities (v(t)). The 4 OB supergiant s ystems in our sample are high-velocity objects (the average value of v (t) is greater than 60 km/s), while the 13 Be systems have low velocit ies (<v(t)> = 11.3 +/- 6.7 km/s), suggesting a different formation mec hanism for the two subgroups. The unusual X-ray/radio source LSI+61 de grees 303 lies much closer than previously believed and its low optica l luminosity (M-v = +2.2) and blue intrinsic colors now suggest it may be a peculiar type of low-mass X-ray binary.