TY - JOUR

T1 - Post-Newtonian models of binary neutron stars

AU - Lombardi, James C.

AU - Rasio, Frederic A.

AU - Shapiro, Stuart L.

N1 - Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.

PY - 1997

Y1 - 1997

N2 - Using an energy variational method, we calculate quasiequilibrium configurations of binary neutron stars modeled as compressible triaxial ellipsoids obeying a polytropic equation of state. Our energy functional includes terms both for the internal hydrodynamics of the stars and for the external orbital motion. We add the leading post-Newtonian (PN) corrections to the internal and gravitational energies of the stars, and adopt hybrid orbital terms which are fully relativistic in the test-mass limit and always accurate to PN order. The total energy functional is varied to find quasiequilibrium sequences for both corotating and irrotational binaries in circular orbits. We examine how the orbital frequency at the innermost stable circular orbit depends on the polytropic index [Formula presented] and the compactness parameter [Formula presented]. We find that, for a given [Formula presented], the innermost stable circular orbit along an irrotational sequence is about 17% larger than the innermost secularly stable circular orbit along the corotating sequence when [Formula presented], and 20% larger when [Formula presented]. We also examine the dependence of the maximum neutron star mass on the orbital frequency and find that, if PN tidal effects can be neglected, the maximum equilibrium mass increases as the orbital separation decreases.

AB - Using an energy variational method, we calculate quasiequilibrium configurations of binary neutron stars modeled as compressible triaxial ellipsoids obeying a polytropic equation of state. Our energy functional includes terms both for the internal hydrodynamics of the stars and for the external orbital motion. We add the leading post-Newtonian (PN) corrections to the internal and gravitational energies of the stars, and adopt hybrid orbital terms which are fully relativistic in the test-mass limit and always accurate to PN order. The total energy functional is varied to find quasiequilibrium sequences for both corotating and irrotational binaries in circular orbits. We examine how the orbital frequency at the innermost stable circular orbit depends on the polytropic index [Formula presented] and the compactness parameter [Formula presented]. We find that, for a given [Formula presented], the innermost stable circular orbit along an irrotational sequence is about 17% larger than the innermost secularly stable circular orbit along the corotating sequence when [Formula presented], and 20% larger when [Formula presented]. We also examine the dependence of the maximum neutron star mass on the orbital frequency and find that, if PN tidal effects can be neglected, the maximum equilibrium mass increases as the orbital separation decreases.

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U2 - 10.1103/PhysRevD.56.3416

DO - 10.1103/PhysRevD.56.3416

M3 - Article

AN - SCOPUS:0000758809

VL - 56

SP - 3416

EP - 3438

JO - Physical Review D - Particles, Fields, Gravitation and Cosmology

JF - Physical Review D - Particles, Fields, Gravitation and Cosmology

SN - 1550-7998

IS - 6

ER -