Observatoire de Haute-Provence, CNRS, F-04870 Saint-Michel l'Observatoire, France E-mail:chevalier@obs-hp.fr
Abstract We present results on parallaxes, magnitudes and proper motions for 17 optically identified massive X-ray binaries (MXRB) which were observed during the Hipparcos astrometry mission. This sample includes the sources detected in the medium-energy range (2-10 keV) having optical counterparts brighter than V=12. We compare the Hipparcos results with ground-based optical data and derive probable values for absolute magnitudes and peculiar tangential velocities (vt). The 4 OB supergiant systems in our sample are high-velocity objects (the average value of vt is greater than 60 km/s), while the 13 Be systems have low velocities (<vt> = 11.3 ± 6.7 km/s), suggesting a different formation mechanism for the two subgroups. The unusual X-ray/radio source LSI+61°303 lies much closer than previously believed and its low optical luminosity (Mv= +2.2) and blue intrinsic colors now suggest it may be a peculiar type of low-mass X-ray binary.
Keywords: Stars: distances -- Stars: kinematics -- Stars: Be -- Stars : binaries: close -- X-rays: stars