Identifying and characterising open clusters

Star clusters are interesting laboratories for studies related to star formation, binary and single stellar evolution, and stellar dynamics. It is necessary to identify cluster member stars and subsequently characterise the global cluster properties including age, metallicity, and extinction for all such studies. Using proper motion and parallax data in Gaia’s eDR3 we have developed a novel non-parametric method to determine membership probability of Galactic open clusters. We have applied this technique to eighteen relatively rich (N>500) open clusters. Our method works well for clusters located in both sparse and crowded environments. Once membership is ascertained in each identified star cluster, we use Bayesian parameter estimation to determine cluster properties such as age, metallicity, and extinction. Because of our Bayesian approach our estimates not only include the fiducial property values, usually found in other similar studies, but also the detailed posterior distributions and correlations. I will explain our approach and show our latest results in my talk.