Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Gamma-ray bursts from accreting black holes in neutron star mergers   By means of three-dimensional hydrodynamic simulations with a Eulerian PPM
code we investigate the formation and the properties of the accretion torus
around the stellar mass black hole which originates from the merging of two
neutron stars. The simulations are performed with four nested cartesian grids
which allow for both a good resolution near the central black hole and a large
computational volume. They include the use of a physical equation of state as
well as the neutrino emission from the hot matter of the torus. The gravity of
the black hole is described with a Newtonian and alternatively with a
Paczynski-Wiita potential. In a post-processing step, we evaluate our models
for the energy deposition by nu-nubar annihilation around the accretion torus.
Our models show that nu-nubar annihilation can yield the energy to account for
weak, short gamma-ray bursts, if moderate beaming is involved. In fact, the
barrier of the dense baryonic gas of the torus suggests that the low-density
pair-photon-plasma is beamed as axial jets into a fraction 2 delta Omega/ (4
pi) between 1/100 and 1/10 of the sky, corresponding to opening half-angles of
roughly ten to several tens of degrees. Thus gamma-burst energies of
10^{50}--10^{51} erg seem within the reach of our models (if the source is
interpreted as radiating isotropically), corresponding to luminosities around
10^{51} erg/s for typical burst durations of 0.1--1 s. Gravitational capture of
radiation by the black hole, redshift and ray bending do not reduce the jet
energy significantly. Effects associated with the Kerr character of the rapidly
rotating black hole, however, could increase the gamma-burst energy
considerably, and effects due to magnetic fields might even be required to get
the energies for long complex gamma-ray bursts.

16
The categories of this paper are: stat
33
The categories of this paper are: plasm-ph
34
The categories of this paper are: chem-ph
20
The categories of this paper are: acc-phys
15
The categories of this paper are: nucl-ex
1
The categories of this paper are: cs
11
The categories of this paper are: hep-lat
37
The categories of this paper are: supr-con
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The categories of this paper are: eess
12
The categories of this paper are: nucl-th
14
The categories of this paper are: math-ph
27
The categories of this paper are: comp-gas
13
The categories of this paper are: quant-ph
10
The categories of this paper are: q-bio
4
The categories of this paper are: cond-mat
23
The categories of this paper are: solv-int