Internal kinematics and binarity of X-ray stars in the Pleiades open cluster

The classical convergent point analysis is implemented for the Pleiades stars with proper motions in the Tycho-2 Catalogue and X-ray fluxes measured by the ROSAT satellite. It is demonstrated that, with the standard astrometric errors as given in Tycho-2, strong X-ray sources in the cluster (logLX > 29:1, where LX is in erg s 1 ) exhibit a velocity dispersion in one component of only 0:20 km s 1 , while the distributions of velocity components of moderate (logLX 10 AU).