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Shibata, Masaru; Uryū, Kōji

doi:10.1103/physrevd.61.064001

Cited by 310 publications

(384 citation statements)

References 44 publications

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“…A high density halo would have to be expected if, for example, the collapse to a black hole were delayed due to the effects of very rapid (differential) rotation or viscous heating (e.g., Duez et al 2004;Morrison et al 2004), in which case the hot neutron star would radiate neutrinos and a neutrino-driven wind (e.g., Duncan et al 1986) would lead to a dense, expanding baryonic cloud around the merger site. It may also be possible to find situations where the accretion torus is surrounded by a thin, dilute halo, in particular, if the BH forms during the merger or within a few dynamical timescales afterwards (e.g., Shibata & Uryū 2000;Shibata et al 2003;Oechslin et al 2004). In regard of these considerations we have performed two series of simulations.…”

Section: Resultsmentioning

confidence: 99%

Relativistic outflows from remnants of compact object mergers and their viability for short gamma-ray bursts

Aloy¹,

Janka²,

Müeller³

2005

A&A

249

291

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Abstract. We present the first general relativistic hydrodynamic models of the launch and evolution of relativistic jets and winds, driven by thermal energy deposition, possibly due to neutrino-antineutrino annihilation, in the close vicinity of black hole-accretion torus systems. The latter are considered to be the remnants of compact object mergers. Our two-dimensional simulations establish the link between models of such mergers and future observations of short gamma-ray bursts by the SWIFT satellite. They show that ultrarelativistic outflow with maximum terminal Lorentz factors around 1000 develops for polar energy deposition rates above some 10 48 erg s −1 per steradian, provided the merger environment has a sufficiently low baryon density. By the interaction with the dense accretion torus the ultrarelativistic outflow with Lorentz factors Γ above 100 is collimated into a sharp-edged cone that is embedded laterally by a wind with steeply declining Lorentz factor. The typical semi-opening angles of the Γ > 100 cone are 5 • −10 • , corresponding to about 0.4−1.5% of the hemisphere and apparent isotropized energies (kinetic plus internal) up to ≈10 51 erg although at most 10−30% of the deposited energy is transferred to the outflow with Γ > 100. The viability of post-merger black hole-torus systems as engines of short, hard gamma-ray bursts is therefore confirmed. The annihilation of neutrino-antineutrino pairs radiated from the hot accretion torus appears as a suitable energy source for powerful axial outflow even if only ≈10 49 erg are deposited within a cone of 45 • half-opening angle around the system axis. Although the torus lifetimes are expected to be only between some 0.01 s and several 0.1 s, our models can explain the durations of all observed short gamma-ray bursts, because different propagation velocities of the front and rear ends will lead to a radial stretching of the ultrarelativistic fireball before transparency is reached. The ultrarelativistic flow reveals a highly non-uniform structure caused by the action of Kelvin-Helmholtz instabilities that originate at the fireball-torus interface. Large radial variations of the baryon density (up to several orders of magnitude) are uncorrelated with moderate variations of the Lorentz factor (factors of a few) and fluctuations of the gently declining radiation-dominated pressure. In the angular direction the Lorentz factor reveals a nearly flat plateau-like maximum with values of several hundreds, that can be located up to 7 • off the symmetry axis, and a steep decrease to less than 10 for polar angles larger than 15 • −20 • . Lateral expansion of the ultrarelativistic core of the flow is prevented by a subsonic velocity component of about 0.05c towards the symmetry axis, whereas the moderately relativistic wings show a subsonic sideways inflation with less than 0.07c (measured in the frame comoving with the radial flow).

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Section: Resultsmentioning

confidence: 99%

Relativistic outflows from remnants of compact object mergers and their viability for short gamma-ray bursts

Aloy¹,

Janka²,

Müeller³

2005

A&A

249

291

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“…Differential rotation can also arise from the mergers of binary neutron stars [4,5,6]. In these new-born, dynamically stable, neutron stars, magnetic fields and/or viscosity will transport angular momentum and cause a substantial change in the configurations on a secular timescale.…”

Section: Introductionmentioning

confidence: 99%

Evolution of magnetized, differentially rotating neutron stars: Simulations in full general relativity

et al. 2006

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We study the effects of magnetic fields on the evolution of differentially rotating neutron stars, which can be formed in stellar core collapse or binary neutron star coalescence. Magnetic braking and the magnetorotational instability (MRI) both act on differentially rotating stars to redistribute angular momentum. Simulations of these stars are carried out in axisymmetry using our recently developed codes which integrate the coupled Einstein-Maxwell-MHD equations. We consider stars with two different equations of state (EOS), a gamma-law EOS with Γ = 2, and a more realistic hybrid EOS, and we evolve them adiabatically. Our simulations show that the fate of the star depends on its mass and spin. For initial data, we consider three categories of differentially rotating, equilibrium configurations, which we label normal, hypermassive and ultraspinning. Normal configurations have rest masses below the maximum achievable with uniform rotation, and angular momentum below the maximum for uniform rotation at the same rest mass. Hypermassive stars have rest masses exceeding the mass limit for uniform rotation. Ultraspinning stars are not hypermassive, but have angular momentum exceeding the maximum for uniform rotation at the same rest mass. We show that a normal star will evolve to a uniformly rotating equilibrium configuration. An ultraspinning star evolves to an equilibrium state consisting of a nearly uniformly rotating central core, surrounded by a differentially rotating torus with constant angular velocity along magnetic field lines, so that differential rotation ceases to wind the magnetic field. In addition, the final state is stable against the MRI, although it has differential rotation. For a hypermassive neutron star, the MHD-driven angular momentum transport leads to catastrophic collapse of the core. The resulting rotating black hole is surrounded by a hot, massive, magnetized torus undergoing quasistationary accretion, and a magnetic field collimated along the spin axis-a promising candidate for the central engine of a short gamma-ray burst.

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“…Similar instabilities have hampered efforts to solve the related problem of binary neutron stars; only very recently [5,6] has there been some success in finding stable algorithms. However, black hole evolutions face an additional obstacle that is absent in the case of neutron stars: for neutron stars the gravitational field is everywhere regular, but for black holes one must somehow deal with the physical singularity that lurks inside each hole.…”

Section: Introductionmentioning

confidence: 99%

Black hole evolution by spectral methods

et al. 2000

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Current methods of evolving a spacetime containing one or more black holes are plagued by instabilities that prohibit long-term evolution. Some of these instabilities may be due to the numerical method used, traditionally finite differencing. In this paper, we explore the use of a pseudospectral collocation (PSC) method for the evolution of a spherically symmetric black hole spacetime in one dimension using a hyperbolic formulation of Einstein's equations. We demonstrate that our PSC method is able to evolve a spherically symmetric black hole spacetime forever without enforcing constraints, even if we add dynamics via a Klein-Gordon scalar field. We find that, in contrast to finite-differencing methods, black hole excision is a trivial operation using PSC applied to a hyperbolic formulation of Einstein's equations. We discuss the extension of this method to three spatial dimensions.04.25.Dm, 02.70.Hm

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Simulation of merging binary neutron stars in full general relativity:Γ=2case

Cited by 310 publications

References 44 publications

Relativistic outflows from remnants of compact object mergers and their viability for short gamma-ray bursts

Relativistic outflows from remnants of compact object mergers and their viability for short gamma-ray bursts

Evolution of magnetized, differentially rotating neutron stars: Simulations in full general relativity

Black hole evolution by spectral methods

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