Journal
CLASSICAL AND QUANTUM GRAVITY
Volume 33, Issue 17, Pages -Publisher
IOP Publishing Ltd
DOI: 10.1088/0264-9381/33/17/175009
Keywords
numerical relativity; gravitational waves; neutron star binaries; Einstein Toolkit
Categories
Funding
- SUMA INFN project
- National Science Foundation in the USA [1212401, 1212426, 1212433, 1212460]
- INFN 'Iniziativa Specifica TEONGRAV'
- 'NewCompStar', COST Action [MP1304]
- Direct For Mathematical & Physical Scien
- Division Of Physics [1212460] Funding Source: National Science Foundation
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We present results from three-dimensional general relativistic simulations of binary neutron star coalescences and mergers using public codes. We considered equal mass models where the baryon mass of the two neutron stars. is 1.4M(circle dot), described by four different equations of state (EOS) for the cold nuclear matter (APR4, SLy, H4, and MS1; all parametrized as piecewise polytropes). We started the simulations from four different initial interbinary distances (40, 44.3, 50, and 60 km), including up to the last 16 orbits before merger. That allows us to show the effects on the gravitational wave (GW) phase evolution, radiated energy and angular momentum due to: the use of different EOS, the orbital eccentricity present in the initial data and the initial separation (in the simulation) between the two stars. Our results show that eccentricity has a major role in the discrepancy between numerical and analytical waveforms until the very last few orbits, where 'tidal' effects and missing high-order post-Newtonian coefficients also play a significant role. We test different methods for extrapolating the GW signal extracted at finite radii to null infinity. We show that an effective procedure for integrating the Newman-Penrose psi(4) signal to obtain the GW strain h is to apply a simple high-pass digital filter to h after a time domain integration, where only the two physical motivated integration constants are introduced. That should be preferred to the more common procedures of introducing additional integration constants, integrating in the frequency domain or filtering psi(4) before integration.
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