Proper motion study of the globular cluster M 3

Abstract

We present proper motions for stars in the field of the galactic globular cluster NGC 5272 (M 3). This study forms part of the Bonn programme of globular cluster proper motions. 14 plates were taken with the Bonn double refractor, spanning epoch differences of up to 85 years. Relative proper motions for all well-measurable stars in the 1.5deg x 1.5deg field covered by the plates were derived. Typical proper motion errors are 0.5-1.2 milliarcsec/year. The cluster membership of UV-bright and variable stars is discussed. The proper motions are compared with the accurate relative proper motions of Cudworth (1979) and with the absolute proper motions from Schmidt plates referred to galaxies of Scholz et al. (1993). The latter comparison enables us to tie the proper motions of the stars and the mean proper motion of M 3 to an inertial system. The absolute proper motions of Hipparcos stars in the field will be useful for an extragalactic calibration of the Hipparcos proper motion system. The data for the 791 stars is available via the CDS (Centre des Donnees Astronomiques Strasbourg) Data Centre.