A proper motion study of the globular cluster M 10

¹ Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, PR China
² National Astronomical Observatories, Chinese Academy of Sciences, PR China
³ Joint Lab for Optical Astronomy, Chinese Academy of Sciences, PR China
⁴ Sternwarte der Universität Bonn, Auf dem Hügel 71, D-53121 Bonn, Germany

Send offprint request to: M. Geffert

Received: 17 September 1999
Accepted: 4 May 2000

Abstract

We present the first proper motion study of M 10 (NGC 6254). Absolute proper motions of about 532 stars in the field of the globular cluster M 10 were determined with respect to Hipparcos and ACT reference stars. In addition to photographic plates of Bonn and Shanghai also wide field CCD observations as second epoch plates were used. The wide field CCD observations show an accuracy comparable to that of the photographic plates. A good coincidence of the solutions based on reference stars from Hipparcos and from ACT was found. Our final proper motions allow a sufficient separation of cluster and field stars. Two population II Cepheids were confirmed to be members of M 10. The absolute proper motion of M 10 was determined and combined with its distance from the Sun and its radial velocity. The space motion and metallicity of M 10 indicates the characteristics of a halo object with an orbit reaching to a maximal z-distance of less than 3 kpc.