Merger of binary neutron stars with realistic equations of state in full general relativity

By M. Shibata, K. Taniguchi, K. Uryū. 2005

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We present numerical results of three-dimensional simulations for the merger of binary neutron stars in full general relativity. Hybrid equations of state are adopted to mimic realistic nuclear equations of state. In this approach, we divide the equations of state into two parts as P=P{sub cold}+P{sub th}. P{sub cold} is the cold part for which we assign a fitting formula for realistic equations of state of cold nuclear matter slightly modifying the formula developed by Haensel and Potekhin. We adopt the SLy and FPS equations of state for which the maximum allowed Arnowitt-Deser-Misner (ADM) mass of cold and spherical neutron stars is {approx_equal}2.04M{sub {center_dot}} and 1.80M{sub {center_dot}}, respectively. P{sub th} denotes the thermal part which is written as P{sub th}=({gamma}{sub th}-1){rho}({epsilon}-{epsilon}{sub cold}), where {rho}, {epsilon}, {epsilon}{sub cold}, and {gamma}{sub th} are the baryon rest-mass density, total specific internal energy, specific internal energy of the cold part, and the adiabatic constant, respectively. Simulations are performed for binary neutron stars of the total ADM mass in the range between 2.4M{sub {center_dot}} and 2.8M{sub {center_dot}} with the rest-mass ratio Q{sub M} to be in the range 0.9 < or approx. Q{sub M}{<=}1. It is found that if the total ADM mass of themore » system is larger than a threshold M{sub thr}, a black hole is promptly formed in the merger irrespective of the mass ratios. In the other case, the outcome is a hypermassive neutron star of a large ellipticity, which results from the large adiabatic index of the realistic equations of state adopted. The value of M{sub thr} depends on the equation of state: M{sub thr}{approx}2.7M{sub {center_dot}} and {approx}2.5M{sub {center_dot}} for the SLy and FPS equations of state, respectively. Gravitational waves are computed in terms of a gauge-invariant wave extraction technique. In the formation of the hypermassive neutron star, quasiperiodic gravitational waves of a large amplitude and of frequency between 3 and 4 kHz are emitted. The estimated emission time scale is < or approx.100 ms, after which the hypermassive neutron star collapses to a black hole. Because of the long emission time, the effective amplitude may be large enough to be detected by advanced laser interferometric gravitational wave detectors if the distance to the source is smaller than {approx}100 Mpc. Thermal properties of the outcome formed after the merger are also analyzed to approximately estimate the neutrino emission energy.« less

Subfields: Astronomy and Astrophysics, Geophysics

View Paper: https://www.semanticscholar.org/paper/79120b5945784e2efed48557079edd18c46d3971

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Citations in the corpus

Physics of strongly magnetized neutron stars (2006, unknown): “…moments of inertia (in the double pulsar system PSR J0737-3039; Lyne et al 2004) and detection of gravitational waves from coalescing neutron star binaries will lead to useful information of neutron star equation of state (e.g. Lai and Wiseman (1996), Faber (et al 2002), Shibata et al (2005)).”
Gravitational waves and non-axisymmetric oscillation modes in mergers of compact object binaries (2011, methodology): “Strong nonaxisymmetric features should be distinguishable in the GW signal and could be used for characterizing the hypermassive compact object (Zhuge et al. 1994; Oechslin et al. 2002; Shibata & Uryū2002; Shibata et al. 2005; Shibata & Taniguchi 2006; Oechslin & Janka 2007; Baiotti et al. 2008; Ki”
Gamma-Ray Bursts in the Swift Era (2007, background): “Dai et al. (2006a) argued for a possible solution of the extended X-ray flares following NS-NS merger GRBs. Numerical simulations have shown that the product of a NS-NS merger may not be a BH (Shibata et al. 2005), if the NS equation-of-state is stiff.”
ELECTROMAGNETIC TRANSIENTS POWERED BY NUCLEAR DECAY IN THE TIDAL TAILS OF COALESCING COMPACT BINARIES (2011, methodology): “The equation of state is a hybrid, where we have combined the cold Friedman-Pandharipande-Skyrme (FPS) nuclear EoS with an ideal thermal compoment as described by Shibata et al. (2005).”
NEUTRINO SIGNATURES AND THE NEUTRINO-DRIVEN WIND IN BINARY NEUTRON STAR MERGERS (2008, background): “1996; Calder & Wang 2002; Faber & Rasio 2002; Shibata & Ury ū 2002; Shibata et al. 2003, 2005; Oechslin & Janka 2007; Anderson et al. 2008b), 2) the production of short-hard GRBs (Ruffert et al. 1997; Ruffert & Janka 1999; Rosswog & Ramirez-Ruiz 2003; Rosswog et al. 2003; Rosswog 2005; Janka et…”
Time-dependent models of accretion discs formed from compact object mergers (2008, background): “However, simulations show that when (and if) collapse actually occurs depends on the mass of the central NS and its ability to transport angular momentum to the surrounding disk (Shibata et al. 2005; Shibata & Taniguchi 2006; Shibata et al. 2006).”
The Einstein Toolkit: a community computational infrastructure for relativistic astrophysics (2011, background): “The first fully general relativistic (GR) simulations of merging NS–NS binaries were reported in 1999, with further advances over the next few years [1–5].”
Binary Neutron Star Mergers: Mass Ejection, Electromagnetic Counterparts, and Nucleosynthesis (2018, background): “If the merger does not result in the formation of a BH within a few dynamical timescales, the remnant is composed of a relatively slowly rotating inner core surrounded by a rotationally supported envelope (Shibata et al. 2005; Kastaun et al. 2016; Ciolfi et al. 2017; Hanauske et al. 2017).”
Relativistic neutron star merger simulations with non-zero temperature equations of state. I. Variation of binary parameters and equation of state (2006, methodology): “…approximation to GR the influence of different microphysical zero-temperature EoSs on the inspiral and merger dynamics, and, on the other hand by Shibata et al. (2005) and Shibata & Taniguchi (2006), who implemented besides full GR an analytic fit to several physical zero-temperature EoSst -…”