The local kinematics of open star clusters.

Data on positions, distances, and radial velocities of 106 open star clusters available from the computer-based catalogue of open clusters prepared by Lyngå have been used in a statistical analysis of the local kinematics. The authors find a velocity field that deviates significantly from circular streaming. The dispersion of the radial velocity residuals increases with age: for the old clusters it is about twice that for young clusters. This may be a further evidence of heating of the galactic disk. The relatively low velocity residuals of the very oldest clusters are explained as a bias due to the disruption of open clusters.