Photometric Study and Detection of Variable Stars in the Open Clusters - I : NGC 6866

TL;DR

This study identifies 28 variable stars in the open cluster NGC 6866, including new discoveries, and analyzes the cluster's physical properties through photometry, revealing its size, reddening, distance, and age.

Contribution

It provides the first comprehensive variability survey of NGC 6866, discovering new variable stars and combining photometric analysis to determine cluster parameters.

Findings

28 periodic variables identified, 19 new discoveries

Cluster has a radius of about 3 parsecs

Estimated age of approximately 630 million years

Abstract

We present results of a variability search in the intermediate-age open cluster NGC 6866 from 29 nights over two observing seasons. We find 28 periodic variables, of which 19 are newly identified. The periods of these variables, which have V magnitudes from 11.5 to 19.3 mag, range from ~ 48 min to 37 d. We detected several delta-Scuti stars, some of which are of high amplitude, as well as gamma-Doradus, rotational variables and eclipsing binaries. In order to study the physical properties of the cluster, we obtained UBVRI photometry of all the stars on a good photometric night. The radial distribution of the stellar surface density shows that the cluster has a radial extent of about 7 arcmin (~3 pc) with a peak density of 5.7+/-0.7 stars/arcmin^2 at the cluster center. The colour-colour diagram indicates a reddening of E(B-V) = 0.10 mag towards NGC 6866. A distance of ~ 1.47 kpc and an age of ~ 630 Myr is estimated from the colour-magnitude diagram using the theoretical isochrones of solar metallicity.