158 research outputs found
A population of binaries in the Asymptotic Giant Branch of 47 Tucanae?
We have used a set of archived Hubble Space Telescope/ACS images to probe the
evolved populations of the globular cluster 47 Tucanae. We find an excess of
Asymptotic Giant Branch (AGB) stars in the cluster core. We interpret this
feature as the signature of an extra-population likely made by the progeny of
massive stars originated by the evolution of binary systems. Indeed the
comparison with theoretical tracks suggests that the AGB population of 47 Tuc
can be significantly contaminated by more massive stars currently experiencing
the first ascending Red Giant Branch.Comment: 14 pages, 4 figures, in press on ApJ Letter
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 () that can be easily measured
when the cumulative radial distribution of these stars and a reference
population are available. Our simulations show that might also be used as
an approximate indicator of the time remaining to the core collapse of the
visible component.Comment: ApJ accepte
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