Longterm general relativistic simulation of binary neutron stars collapsing to a black hole

Abstract

General relativistic simulations for the merger of binary neutron stars are performed as an extension of a previous work\cite{Shibata:2006nm}. We prepare binary neutron stars with a large initial orbital separation and employ the moving-puncture formulation, which enables to follow merger and ringdown phases for a long time, even after black hole formation. For modeling inspiraling neutron stars, which should be composed of cold neutron stars, the Akmal-Pandhalipande-Ravenhall (APR) equation of state (EOS) is adopted. After the onset of the merger, the hybrid-type EOS is used; i.e., the cold and thermal parts are given by the APR and $\Gamma$-law EOSs, respectively. Three equal-mass binaries each with mass $1.4M_{\odot },1.45M_{\odot },1.5M_{\odot }$ and two unequal-mass binaries with mass 1.3--$1.6M_{\odot }$, 1.35--$1.65M_{\odot }$ are prepared. We focus primarily on the black hole formation case, and explore mass and spin of the black hole, mass of disks which surround the black hole, and gravitational waves emitted during the black hole formation. We find that (i) for the systems of $m_0=2.9$--$3.0M_{\odot }$ and of mass ratio $\approx 0.8$, the mass of disks which surround the formed black hole is 0.006--$0.02M_{\odot }$; (ii) the spin of the formed black hole is $0.78\pm 0.02$ when a black hole is formed after the merger in the dynamical time scale. This value depends weakly on the total mass and mass ratio, and is about 0.1 larger than that of a black hole formed from nonspinning binary black holes; (iii) for the black-hole formation case, Fourier spectrum shape of gravitational waves emitted in the merger and ringdown phases has a universal qualitative feature irrespective of the total mass and mass ratio, but quantitatively, the spectrum reflects the parameters of the binary neutron stars.

35 pages, 20 figures, accepted to PRD

References in corpus (26)

• Gamma-Ray Bursts: Progress, Problems & Prospects
• Inspiral, merger and ring-down of equal-mass black-hole binaries
• Calibration of Moving Puncture Simulations
• Accurate evolutions of inspiralling neutron-star binaries: prompt and delayed collapse to black hole
• High-accuracy waveforms for binary black hole inspiral, merger, and ringdown
• Simulating coalescing compact binaries by a new code SACRA
• Reducing orbital eccentricity in binary black hole simulations
• Exploring black hole superkicks
• General relativistic simulations of magnetized binary neutron star mergers
• Analytical representations of unified equations of state of neutron-star matter
• Where post-Newtonian and numerical-relativity waveforms meet
• Magnetorotational collapse of massive stellar cores to neutron stars: Simulations in full general relativity
• Consistency of post-Newtonian waveforms with numerical relativity
• High-accuracy numerical simulation of black-hole binaries: Computation of the gravitational-wave energy flux and comparisons with post-Newtonian approximants
• Simulating binary neutron stars: dynamics and gravitational waves
• Merger of black hole-neutron star binaries in full general relativity
• Merger of black hole and neutron star in general relativity: Tidal disruption, torus mass, and gravitational waves
• Circularization and Final Spin in Eccentric Binary Black Hole Inspirals
• Comparison between numerical-relativity and post-Newtonian waveforms from spinning binaries: the orbital hang-up case
• Merger of black hole-neutron star binaries: nonspinning black hole case
• Eccentric binary black-hole mergers: The transition from inspiral to plunge in general relativity
• Reducing eccentricity in black-hole binary evolutions with initial parameters from post-Newtonian inspiral
• Magnetohydrodynamics of Neutrino-Cooled Accretion Tori around a Rotating Black Hole in General Relativity
• Status of black-hole-binary simulations for gravitational-wave detection
• Comparison of high-accuracy numerical simulations of black-hole binaries with stationary phase post-Newtonian template waveforms for Initial and Advanced LIGO
• Comparison between numerical relativity and a new class of post-Newtonian gravitational-wave phase evolutions: the non-spinning equal-mass case