NGC 6749 : a metal-poor halo globular in a disc field rich in mira variables

Abstract

We present V, I photometry of the loose star cluster NGC 6749, and for the first time colour-magnitude diagrams are provided. We confirm that it is a globular cluster and its blue horizontal branch indicates that it is metal-poor. We derive a reddening of E(B - V) = 1.39 ± 0.04 and a distance from the Sun d̛ = 7.3 ± 0.9 kpc (assuming a total-to-selective absorption R = 3.4). The cluster is projected very close to the Galactic plane, and the derived distance implies a Galactic coordinate Z ~~ - 300 pc. lt is thus a halo globular cluster located close to the disc plane. We also discuss the properties of 78 newly discovered long-period variable stars, of which 75 are Miras, projected within 1º of the cluster centre. The variables do not appear to be associated with the globular cluster. From their periods, most of them belong to the metal-rich disc or bulge stellar populations.