Blue Stragglers as tracers of the dynamical state of two clusters in the
  Small Magellanic Cloud: NGC 339 and NGC 419
  The level of central segregation of Blue Straggler stars proved to be an
excellent tracer of the dynamical evolution of old star clusters (the so-called
"dynamical clock"), both in the Milky Way and in the Large Magellanic Cloud.
The $A^{+}$ parameter, used to measure the Blue Stragglers degree of
segregation, has in fact been found to strongly correlate with the parent
cluster central relaxation time. Here we studied the Blue-Straggler population
of two young stellar systems in the Small Magellanic Cloud, namely NGC 339
(which is 6 Gyr old) and NGC 419 (with an age of only 1.5 Gyr), in order to
study their dynamical state. Thanks to multi-epoch, high angular resolution
Hubble Space Telescope observations available for both clusters, we took
advantage of the stellar proper motions measured in the regions of the two
systems and we selected a population of likely cluster members, removing the
strong contamination from Small Magellanic Cloud stars. This enabled us to
study, with unprecedented accuracy, the radial distribution of Blue Stragglers
in these two extragalactic clusters and to measure their dynamical age. As
expected for such young clusters, we found that both systems are poorly evolved
from the dynamical point of view, also fully confirming that the $A^{+}$
parameter is a sensitive "clock hand" even in the dynamically-young regime.
