Investigating mass segregation process in globular clusters with Blue   Straggler Stars: the impact of dark remnants
  We present the results of a set of N-body simulations aimed at exploring how the process of mass segregation (as traced by the spatial distribution of blue straggler stars, BSSs) is affected by the presence of a population of heavy dark remnants (as neutron stars and black holes). To this end, clusters characterized by different initial concentrations and different fractions of dark remnants have been modeled. We find that an increasing fraction of stellar-mass black holes significantly delays the mass segregation of BSSs and the visible stellar component. In order to trace the evolution of BSS segregation, we introduce a new parameter ($A^+$) that can be easily measured when the cumulative radial distribution of these stars and a reference population are available. Our simulations show that $A^+$ might also be used as an approximate indicator of the time remaining to the core collapse of the visible component. 
Emiliano Alessandrini, Barbara Lanzoni, Francesco Rosario Ferraro,   Paolo Miocchi, Enrico Vesperini
astro-ph.GA astro-ph.SR