Radial velocities and membership of stars in the old, distant open cluster Berkeley 29

Abstract

Multi slit spectroscopy at the Telescopio Nazionale Galileo was employed to measure radial velocities for 20 stars in the direction of the old open cluster Berkeley 29, the farthest known in our Galaxy. Membership information was derived for stars all along the red giant branch, in particular near its tip, and on the red clump. The sample of bona fide cluster members was used to revise the cluster distance to ∼15 kpc, on the basis of an empirical comparison with the red clump in open clusters with known distances. A metallicity [Fe/H] = -0.74 ± 0.18 was also estimated using the colours of spectroscopically confirmed red giant stars.