Hubble Space Telescope proper motion (HSTPROMO) catalogs of Galactic globular clusters. IV. Kinematic profiles and average masses of blue straggler stars
A. T. Baldwin (1, 2), L. L. Watkins (2), R. P. van der Marel (2), P., Bianchini (3), A. Bellini (2), J. Anderson (2) ((1) Louisiana State, (2), STScI, (3) MPIA)

TL;DR
This study uses Hubble Space Telescope data to analyze the kinematic profiles and estimate the average masses of blue straggler stars in Galactic globular clusters, revealing they are more massive than typical stars and consistent with previous measurements.
Contribution
First to derive radial velocity-dispersion profiles for BSSs in GCs and estimate their average masses using energy equipartition principles and recent simulations.
Findings
BSSs have lower velocity dispersions than main-sequence turnoff stars.
Estimated average BSS mass is approximately 1.22 solar masses.
Results agree with previous individual mass measurements of BSSs.
Abstract
We make use of the Hubble Space Telescope proper-motion catalogs derived by Bellini et al. (2014) to produce the first radial velocity-dispersion profiles sigma(R) for blue straggler stars (BSSs) in Galactic globular clusters (GCs), as well as the first dynamical estimates for the average mass of the entire BSS population. We show that BSSs typically have lower velocity dispersions than stars with mass equal to the main-sequence turnoff mass, as one would expect for a more massive population of stars. Since GCs are expected to experience some degree of energy equipartition, we use the relation sigma~M^-eta, where eta is related to the degree of energy equipartition, along with our velocity-dispersion profiles to estimate BSS masses. We estimate eta as a function of cluster relaxation from recent Monte Carlo cluster simulations by Bianchini et al. (2016b) and then derive an average mass…
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