Hubble Space Telescope proper motion (HSTPROMO) catalogs of Galactic
  globular clusters. IV. Kinematic profiles and average masses of blue
  straggler stars
  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 ratio M_BSS
/M_MSTO=1.50+/-0.14 and an average mass M_BSS=1.22+/-0.12 M_Sun from 598 BSSs
across 19 GCs. The final error bars include any systematic errors that are
random between different clusters, but not any potential biases inherent to our
methodology. Our results are in good agreement with the average mass of
M_BSS=1.22+/-0.06 M_Sun for the 35 BSSs in Galactic GCs in the literature with
properties that have allowed individual mass determination.
