Jasonjot Singh Kalirai
University of California Observatories/Lick Observatory, University of California at Santa Cruz,
1156 High Street, Santa Cruz, California 95064, USA
Abstract. We derive the age, distance, reddening, binary fraction, metallicity, and star formation rate for the rich open star cluster NGC 2099 by comparing a high quality observational colour-magnitude diagram (CMD) with synthetic CMDs based on MonteCarlo numerical simulations. This approach accounts for all of the main parameters which determine the shape of the CMD for a stellar population and, unlike theoretical isochrone fits, allows a detailed comparison of the number of stars in various evolutionary phases. The resulting parameters are a key input into determining how much mass stars in NGC 2099 have lost through post main-sequence evolution. We follow up our deep imaging study with multi-object spectroscopy of ~20 cluster white dwarf stars and constrain the initial-final mass relationship. The results clearly indicate that stars with initial masses between 2.8 and 3.4 MOdot lose 70-75% of their mass through stellar evolution. For the first time, we find some evidence for a metallicity dependence on the initial-final mass relationship.
Keywords: colour-magnitude diagrams -- open clusters and associations: individual (NGC 2099) -- stars: evolution -- techniques: spectroscopic -- white dwarfs