S316p.108 — Characterizing Blue Straggler Star Populations in Globular Clusters using HST Photometric Survey Data and Spectroscopy

Date & Time

Aug 10th at 6:00 PM until 7:30 PM




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Author(s): Mirko Simunovic1, Thomas Hyazinth Puzia1

Institution(s): 1. Pontificia Universidad Catolica de Chile

Blue Straggler Stars (BSSs) have been recently found to trace the evolution of their parent globular clusters (GC). BSS formation is believed to be linked to strong dynamical interactions involving binary and/or single stars which may also depend on the larger dynamical state of their parent system. We have combined HST/ACS optical and HST/WFC3 near-UV photometric archival data of the inner regions for over 50 galactic GCs. Using proper motion cleaning of the color-magnitude diagrams (CMD) we have constructed a large homogenous catalog of BSSs in the core of GCs and studied their CMD location properties. We further use a set of stellar evolutionary models to find interpolated stellar mass and age estimates for the BSS populations in all GCs in order to parametrize their physical properties. Different mass and age distributions can be used to constrain the conditions of BSS formation for varying cluster parameters such as metallicity and core structure. Moreover, we try to use multiple parameters such as the binary fraction, binary mass ratio and stellar collision rate to explore the resulting BSS mass and age distributions, and in this way shed light on their progenitors and formation scenarios. Additional spectroscopic data for selected GCs provide direct input and complements our BSS photometric characterization, including an apparent correlation between BSS rotational velocity and our BSS mass estimate. We discuss our findings in the context of the predictions from Monte Carlo evolutionary simulations of GCs.