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

Abstract

We present the VI CCD photometric observations of about 5500 stars up to a limiting magnitude of V ~20 in an area of ~16' × 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.