OPEN CLUSTERS IN THE KEPLER FIELD. II. NGC 6866

摘要

We have developed a maximum-likelihood procedure to fit theoretical isochrones to the observed cluster color-magnitude diagrams of NGC 6866, an open cluster in the Kepler spacecraft field of view. The Markov chain Monte Carlo algorithm permits exploration of the entire parameter space of a set of isochrones to find both the best solution and the statistical uncertainties. For clusters in the age range of NGC 6866 with few, if any, red giant members, a purely photometric determination of the cluster properties is not well-constrained. Nevertheless, based on our UBVRI photometry alone, we have derived the distance, reddening, age, and metallicity of the cluster and established estimates for the binary nature and membership probability of individual stars.We derive the following values for the cluster properties: (m - M)_V = 10.98 ± 0.24, E(B - V ) = 0.16 ± 0.04 (so the distance = 1250 pc), age = 705 ± 170 Myr, and Z = 0.014 ± 0.005.