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 catalogue 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 …