White dwarfs and the ages of open clusters

Open clusters have long been objects of interest in astronomy. As a good approximation of essentially pure stellar populations, they have proved very useful for studies in a wide range of astrophysically interesting questions, including stellar evolution and atmosphere, the chemical and dynamical evolution of our Galaxy, and the structure of our Galaxy. Of fundamental importance to our understanding of open clusters, as well as many other questions in astrophysics, is the accurate determination of ages. Currently there are two main techniques for independently determining the ages of stellar populations: main sequence evolution theory (via cluster isochrones) and white dwarf cooling theory. Open clusters provide the ideal environment for the calibration of these two important clocks, as well as the unique opportunity to directly compare and refine our understanding of both theories. Here I present a photometric study of six open clusters, including both ground-based data, and new, deep photometric data from the Hubble Space Telescope. From the former I derive main sequence turn off ages, while the latter will be used to search for faint cluster white dwarfs. From these data I measure a white dwarf age for each cluster and directly compare these ages with those I find from the main sequence turn off age. For this analysis I employ a new Bayesian statistical technique that has been developed by our group. Additionally, I use this new technique to explore the feasibility of a new method to determine cluster white dwarf ages from the hot (bright) white dwarfs alone, and its first successful application to the Hyades.