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Published July 15, 2016 | Published
Journal Article Open

How loud are neutron star mergers?

Abstract

We present results from the first large parameter study of neutron star mergers using fully general relativistic simulations with finite-temperature microphysical equations of state and neutrino cooling. We consider equal and unequal-mass binaries drawn from the galactic population and simulate each binary with three different equations of state. Our focus is on the emission of energy and angular momentum in gravitational waves in the postmerger phase. We find that the emitted gravitational-wave energy in the first ∼10  ms of the life of the resulting hypermassive neutron star (HMNS) is about twice the energy emitted over the entire inspiral history of the binary. The total radiated energy per binary mass is comparable to or larger than that of nonspinning black hole inspiral-mergers. About 0.8–2.5% of the binary mass-energy is emitted at kHz frequencies in the early HMNS evolution. We find a clear dependence of the postmerger gravitational wave emission on binary configuration and equation of state and show that it can be encoded as a broad function of the binary tidal coupling constant κ^T_2. Our results also demonstrate that the dimensionless spin of black holes resulting from subsequent HMNS collapse are limited to ≲ 0.7–0.8. This may significantly impact the neutrino pair annihilation mechanism for powering short gamma-ray bursts (sGRB).

Additional Information

© 2016 American Physical Society. (Received 23 December 2015; published 11 July 2016) We thank B. S. Sathyaprakash for triggering this work. This research was partially supported by the Sherman Fairchild Foundation and by NSF under Grants No. CAREER PHY-1151197, No. PHY-1404569, and No. AST-1333520. The simulations were performed on the Caltech computer Zwicky (NSF PHY-0960291), on NSF XSEDE (TG-PHY100033), and on NSF/NCSA Blue Waters (NSF PRAC ACI-1440083). L. R. and P. M. were supported by NASA Einstein Postdoctoral Fellowships under Grants No. PF3-140114 and No. PF5-160140, respectively.

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Published - PhysRevD.94.024023.pdf

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