Absolute Proper Motion and Space Motion of the Globular Cluster M15

Abstract

We have separated cluster members and field stars for stars in a region around the globular cluster M 15. The membership of ultraviolet bright stars of M 15 is discussed. The absolute proper motion of M 15 has been determined with respect to the PPM catalogue. An extragalactic calibration of the proper motions has been performed. The calibration was done by measurements of galaxies on the Palomar Sky Survey glass copies and plates from the Schmidt telescope of the Observatoire de la Cote d'Azur (CERGA). We compare the three different methods of establishing absolute proper motion for the globular cluster M 15. The orbital parameters of M 15 have been derived. As a by-product of our work, we obtained for eight stars of the HIPPARCOS input catalogue absolute proper motions, which may be used for the calibration of the HIPPARCOS proper motion system.