CCD BVRI and 2MASS photometry of the poorly studied open cluster NGC 6631

Abstract

Here we have obtained the BVRI CCD photometry down to a limiting magnitude of V∼20 for the southern poorly studied open cluster NGC 6631. It is observed from the 1.88m Telescope of Kottamia Observatory in Egypt. About 3300 stars have been observed in an area of ∼10′×10′ around the cluster center. The main photometric parameters have been estimated and compared with the results that determined for the cluster using JHKs 2MASS photometric database. The cluster’s diameter is estimated to be 10arcmin; the reddening E(B-V)=0.68±0.10mag, E(J-H)=0.21±0.10mag, the true modulus (m-M)o=12.16±0.10mag, which corresponds to a distance of 2700±125pc and age of 500±50Myr.