Feryal Ozel, Dimitrios Psaltis, Ramesh Narayan, Antonio Santos Villarreal
We investigate the distribution of neutron star masses in different
populations of binaries, employing Bayesian statistical techniques. In
particular, we explore the differences in neutron star masses between sources
that have experienced distinct evolutionary paths and accretion episodes. We
find that the distribution of neutron star masses in non-recycled eclipsing
high-mass binaries as well as of slow pulsars, which are all believed to be
near their birth masses, has a mean of 1.28 M_solar and a dispersion of 0.24
M_solar. These values are consistent with expectations for neutron star
formation in core-collapse supernovae. On the other hand, double neutron stars,
which are also believed to be near their birth masses, have a much narrower
mass distribution, peaking at 1.33 M_solar but with a dispersion of only 0.06
M_solar. Such a small dispersion cannot easily be understood and perhaps points
to a particular and rare formation channel. The mass distribution of neutron
stars that have been recycled has a mean of 1.48 M_solar and a dispersion of
0.2 M_solar, consistent with the expectation that they have experienced
extended mass accretion episodes. The fact that only a very small fraction of
recycled neutron stars in the inferred distribution have masses that exceed ~2
M_solar suggest that only a few of these neutron stars cross the mass threshold
to form low mass black holes.
View original:
http://arxiv.org/abs/1201.1006
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