Wolf-Rayet stars and O-star runaways with HIPPARCOS - I. Kinematics

Reliable systemic radial velocities are almost impossible to secure for Wolf-Rayet stars, difficult for O stars. Therefore, to study the motions - both systematic in the Galaxy and peculiar - of these two related types of hot, luminous star, we have examined the Hipparcos proper motions of some 70 stars of each type. We find that (a) both groups follow Galactic rotation in the same way, (b) both have a similar fraction of "runaways", (c) mean kinetic ages based on displacement and motion away from the Galactic plane tend to slightly favour the cluster ejection over the the binary supernova hypothesis for their formation, and (d) those with significant peculiar supersonic motion relative to the ambient ISM, tend to form bow shocks in the direction of the motion.