Blue straggler formation at core collapse
  Among the most striking feature of blue straggler stars (BSS) is the presence
of multiple sequences of BSSs in the colour-magnitude diagrams (CMDs) of
several globular clusters. It is often envisaged that such a multiple BSS
sequence would arise due a recent core collapse of the host cluster, triggering
a number of stellar collisions and binary mass transfers simultaneously over a
brief episode of time. Here we examine this scenario using direct N-body
computations of moderately massive star clusters (of order 10^4 Msun ). As a
preliminary attempt, these models are initiated with approx. 8-10 Gyr old
stellar population and King profiles of high concentrations, being "tuned" to
undergo core collapse quickly. BSSs are indeed found to form in a "burst" at
the onset of the core collapse and several of such BS-bursts occur during the
post-core-collapse phase. In those models that include a few percent primordial
binaries, both collisional and binary BSSs form after the onset of the (near)
core-collapse. However, there is as such no clear discrimination between the
two types of BSSs in the corresponding computed CMDs. We note that this may be
due to the less number of BSSs formed in these less massive models than that in
actual globular clusters.
