Constraints on blue straggler formation mechanisms in Galactic globular
  clusters from proper motion velocity distributions
  For a sample of 38 Galactic globular clusters (GCs), we confront the observed
distributions of blue straggler (BS) proper motions and masses (derived from
isochrone fitting) from the BS catalog of Simunovic & Puzia with theoretical
predictions for each of the two main competing BS formation mechanisms. These
are mass transfer from an evolved donor on to a main-sequence (MS) star in a
close binary system, and direct collisions involving MS stars during binary
encounters. We use the \texttt{FEWBODY} code to perform simulations of
single-binary and binary-binary interactions. This provides collisional
velocity and mass distributions for comparison to the observed distributions.
Most clusters are consistent with BSs derived from a dynamically relaxed
population, supportive of the binary mass-transfer scenario. In a few clusters,
including all the post-core collapse clusters in our sample, the collisional
velocities provide the best fit.
