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Post-Newtonian smoothed particle hydrodynamics calculations of binary neutron star coalescence. II. Binary mass ratio, equation of state, and spin dependence

Post-Newtonian smoothed particle hydrodynamics calculations of binary neutron star coalescence.... Using our new post-Newtonian SPH (smoothed particle hydrodynamics) code, we study the final coalescence and merging of neutron star (NS) binaries. We vary the stiffness of the equation of state (EOS) as well as the initial binary mass ratio and stellar spins. Results are compared to those of Newtonian calculations, with and without the inclusion of the gravitational radiation reaction. We find a much steeper decrease in the gravity wave peak strain and luminosity with decreasing mass ratio than would be predicted by simple point-mass formulas. For a NS with a softer EOS (which we model as simple Γ = 2 polytropes) we find a stronger gravity wave emission, with a different morphology than for a stiffer EOS (modeled as Γ = 3 polytropes as in our previous work). We also calculate the coalescence of NS binaries with an irrotational initial condition, and find that the gravity wave signal is relatively suppressed compared to the synchronized case, but shows a very significant second peak of emission. Mass shedding is also greatly reduced, and occurs via a different mechanism than in the synchronized case. We discuss the implications of our results for gravity wave astronomy with laser interferometers such as LIGO and for theoretical models of gamma-ray bursts (GRBs) based on NS mergers. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Physical Review D American Physical Society (APS)

Post-Newtonian smoothed particle hydrodynamics calculations of binary neutron star coalescence. II. Binary mass ratio, equation of state, and spin dependence

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References (11)

Publisher
American Physical Society (APS)
Copyright
Copyright © 2001 The American Physical Society
ISSN
1089-4918
DOI
10.1103/PhysRevD.63.044012
Publisher site
See Article on Publisher Site

Abstract

Using our new post-Newtonian SPH (smoothed particle hydrodynamics) code, we study the final coalescence and merging of neutron star (NS) binaries. We vary the stiffness of the equation of state (EOS) as well as the initial binary mass ratio and stellar spins. Results are compared to those of Newtonian calculations, with and without the inclusion of the gravitational radiation reaction. We find a much steeper decrease in the gravity wave peak strain and luminosity with decreasing mass ratio than would be predicted by simple point-mass formulas. For a NS with a softer EOS (which we model as simple Γ = 2 polytropes) we find a stronger gravity wave emission, with a different morphology than for a stiffer EOS (modeled as Γ = 3 polytropes as in our previous work). We also calculate the coalescence of NS binaries with an irrotational initial condition, and find that the gravity wave signal is relatively suppressed compared to the synchronized case, but shows a very significant second peak of emission. Mass shedding is also greatly reduced, and occurs via a different mechanism than in the synchronized case. We discuss the implications of our results for gravity wave astronomy with laser interferometers such as LIGO and for theoretical models of gamma-ray bursts (GRBs) based on NS mergers.

Journal

Physical Review D – American Physical Society (APS)

Published: Feb 15, 2001

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