Binary information from open clusters using SEDs (BINOCS) project: the dynamical evolution of the binary population in cluster environments

Abstract

A majority of stars are formed in open clusters, and then ejected into the Galactic field population through tidal effects from external masses, as well as internal gravitational interactions. Therefore, understanding the internal dynamics of open clusters, through N-Body simulations, will inform the growth of the Galactic stellar population. A major input into these N-Body simulations is the frequency and mass distribution of binary star systems, which are currently based on statistics derived from the field population, but the distributions of binaries in clusters may be different. Current binary detection techniques, such as radial velocity surveys, have drawbacks which limit their usefulness for detailed studies over large mass ranges. As presented in the literature, different mass ranges may produce different interpretations of the observed binary population, e.g, as published recently for NGC 1818. A clearer picture of the binary population, covering a wide mass range, is needed to improve the understanding of cluster binary populations, which will inform cluster simulations. We introduce a new binary detection method, Binary INformation from Open Clusters Using SEDs (BINOCS). Using newly-observed multi-wavelength photometric catalogs (0.3 - 8 micron) of the key open clusters M35, M36, M37, M67 and NGC 2420, the BINOCS method is able to determine accurate component masses for unresolved cluster binaries. We present results on the dynamical evolution of binaries from 0.4 - 2.5 M_sun within these key clusters, and explore how these results change with mass--Abstract.