BN3 - Double Neutron Stars and Neutron Star-White Dwarf Binaries |
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Speaker |
Oliveira, Fernanda |
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Coauthors |
Rueda, Jorge A.; Ruffini, Remo; Cipolletta, Federico; Muccino, Marco |
| Talk Title |
On the fate of neutron star binary mergers |
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Abstract |
A neutron star (NS) binary merger might give origin either to a new massive NS or to a prompt collapse to a black hole (BH) depending if the mass of the post-merger object is lower or higher than the NS critical mass. Both cases might lead to short GRBs and, as pointed out by Ruffini et al. (2015), they have distinct observational features which can be gathered in a sub-classification of short GRBs into two families: family-1burts, with isotropic energies lower than 1E52 erg, are emitted by the formation of a massive NS after during the merger, while family-2 bursts, with isotropic energies higher than 1E52 erg, originate from a black hole (BH) formation. Assuming baryon-mass and angular momentum conservation during the merger, we compute the structure of the post-merger object from the numerical solution of the axially symmetric Einstein equations in full rotation. We evaluate the stability of the post-merger NS with respect to the mass-shedding limit and the secular axisymmetric instability, establishing the value of the mass of the NS binary components over which a BH is formed after the merger. Our results indicate that none of the galactic binary NSs will lead to BH formation after the final merger, and therefore the local rate of high energetic Family-2 short GRBs must be extremely low, much lower than the local rate of binary NSs. The sensitivity of the results on the nuclear equation of state of NSs is discussed. |
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