Binary neutron star mergers: effects of spin and post-merger dynamics. (arXiv:1906.05288v1 [astro-ph.HE])

Binary neutron star mergers: effects of spin and post-merger dynamics. (arXiv:1906.05288v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+East_W/0/1/0/all/0/1">William E. East</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Paschalidis_V/0/1/0/all/0/1">Vasileios Paschalidis</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pretorius_F/0/1/0/all/0/1">Frans Pretorius</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tsokaros_A/0/1/0/all/0/1">Antonios Tsokaros</a>

Spin can have significant effects on the electromagnetic transients
accompanying binary neutron star mergers. The measurement of spin can provide
important information about binary formation channels. In the absence of a
strong neutron star spin prior, the degeneracy of spin with other parameters
leads to significant uncertainties in their estimation, in particular limiting
the power of gravitational waves to place tight constraints on the nuclear
equation of state. Thus detailed studies of highly spinning neutron star
mergers are essential to understand all aspects of multimessenger observation
of such events. We perform a systematic investigation of the impact of neutron
star spin—considering dimensionless spin values up to $a_{rm NS}=0.33$—on
the merger of equal mass, quasicircular binary neutron stars using fully
general-relativistic simulations. We find that the peak frequency of the
post-merger gravitational wave signal is only weakly influenced by the neutron
star spin, with cases where the spin is aligned (anti-aligned) with the orbital
angular momentum giving slightly lower (higher) values compared to the
irrotational case. We find that the one-arm instability arises in a number of
cases, with some dependence on spin. Spin has a pronounced impact on the mass,
velocity, and angular distribution of the dynamical ejecta, and the mass of the
disk that remains outside the merger remnant. We discuss the implications of
these findings on anticipated electromagnetic signals, and on constraints that
have been placed on the equation of state based on multimessenger observations
of GW170817.

Spin can have significant effects on the electromagnetic transients
accompanying binary neutron star mergers. The measurement of spin can provide
important information about binary formation channels. In the absence of a
strong neutron star spin prior, the degeneracy of spin with other parameters
leads to significant uncertainties in their estimation, in particular limiting
the power of gravitational waves to place tight constraints on the nuclear
equation of state. Thus detailed studies of highly spinning neutron star
mergers are essential to understand all aspects of multimessenger observation
of such events. We perform a systematic investigation of the impact of neutron
star spin—considering dimensionless spin values up to $a_{rm NS}=0.33$—on
the merger of equal mass, quasicircular binary neutron stars using fully
general-relativistic simulations. We find that the peak frequency of the
post-merger gravitational wave signal is only weakly influenced by the neutron
star spin, with cases where the spin is aligned (anti-aligned) with the orbital
angular momentum giving slightly lower (higher) values compared to the
irrotational case. We find that the one-arm instability arises in a number of
cases, with some dependence on spin. Spin has a pronounced impact on the mass,
velocity, and angular distribution of the dynamical ejecta, and the mass of the
disk that remains outside the merger remnant. We discuss the implications of
these findings on anticipated electromagnetic signals, and on constraints that
have been placed on the equation of state based on multimessenger observations
of GW170817.

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