Mean proper motions of 112 open clusters from all over the sky and within 1 kpc were determined using the data provided by the Tycho2 Catalogue. Applying the statistical method of Sanders (1971) we asserted the membership of 4006 stars and we determined for the first time mean proper motions of 28 clusters.
A comparison of our results with those of BDW showed that both sets are in agreement. In a few cases with discrepant results, we could show that the differences were real differences between Tycho2 and Hipparcos, or due to the too small numbers of stars considered by BDW. Similar conclusions were obtained from comparisons with other studies involving smaller number of clusters in the literature. These comparisons make us confident that the proper motions derived for the first time are correct, and provide a useful confirmation of BDW results, using a larger sample of stars.
Acknowledgements
We would like to thank to Paula Coelho for the collaboration in the computational problems and Dr. Roberto Boczko and Julio Camargo for the helpful hints. We also thank the referee Dr. J. Kovalevsky for the suggestions, to Dra. Elena Glushkova and Dr. Holger Baumgardt for the comments and discussions about this work. Extensive use has been made of the Simbad and BDA databases. This project was supported by FAPESP (grant number 99/11781-4).
Copyright ESO 2001