Binary Neutron Stars

Binary Neutron Stars in General Relativity

University of Illinois at Urbana-Champaign

The equations of general relativity are solved to determine the equilibrium profiles of identical neutron stars in quasi-stationary circular orbit. The stars are each supported by a polytropic equation of state with adiabatic index Gamma = 2. The calculated central density of the stars decreases with decreasing binary separation. We find no tendency to collapse to black holes before the merger. This has important implications for the detection of gravitational waves from binary merger.

Evolution to Contact Binary

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Binary neutron stars are evolved numerically until they touch. We view them from above the orbital plane. The colorbar on the left indicates the density of the neutron star. The arrow points to the central density. As the stars approach, the central density decreases, suggesting that no black holes will form before the complete merger of the neutron stars. Each neutron star has a radius of 5.7 M0, where M0 is the rest mass. The initial separation of the neutron stars is 12 M0. The innermost stable circular orbit occurs when the stars' surfaces are separated by a distance of 3.74 M0.

Generation of Gravitational Waves

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Here, we see numerical simulations of gravitational waves due to the inspiral of the binary system. These calculations used the point-mass quadrapole approximation, but the quasi-equilibrium models were computed in full general relativity. These waves are being viewed from a plane perpendicular to the orbital plane of the neutron stars. Here, brighter colors represent higher amplitude.

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Another representation of the gravitational waves in the equatorial plane, where height represents the gravitational wave amplitude.

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University of Illinois at Urbana-Champaign

last updated 3 Nov 14 by aakhan3

Center for Theoretical Astrophysics---University of Illinois at Urbana-Champaign

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