A deep V I CCD photometric study of the neglected galactic star cluster NGC 6631

Abstract

We present the V I CCD photometric observations of about 5500 stars up to a limiting magnitude of V ~ 20 in an area of ~ 16? x 16? around the cluster NGC 6631. The cluster parameters determined for the first time by fitting the theoretical isochrones in the V, (V - I) diagram of the cluster stars are E (V - I) = 0.60 +/- 0.05 mag, distance = 2.6 +/- 0.5 kpc, age = 400 +/- 100 Myr and metallicity, Z = 0.05. The cluster diameter determined from the radial density profile is 4.8 +/- 0.5 pc. The mass function of the cluster has a slope of 2.1 +/- 0.5.