2003MNRAS.345.1077R -
Mon. Not. R. Astron. Soc., 345, 1077-1090 (2003/November-2)
High-resolution calculations of merging neutron stars - III. Gamma-ray bursts.
ROSSWOG S., RAMIREZ-RUIZ E. and DAVIES M.B.
Abstract (from CDS):
Recent three-dimensional, high-resolution simulations of neutron star coalescences are analysed to assess whether short gamma-ray bursts (GRBs) could originate from such encounters. The two most popular modes of energy extraction - namely the annihilation of {formmu1} and magnetohydrodynamic processes - are explored in order to investigate their viability in launching GRBs. We find that {formmu2} annihilation can provide the necessary stresses to drive a highly relativistic expansion. However, unless the outflow is beamed into less than 1 per cent of the solid angle, this mechanism may fail to explain the apparent isotropized energies implied for short GRBs at cosmological distances. We argue that the energetic, neutrino-driven wind that accompanies the merger event will have enough pressure to provide adequate collimation to the {formmu3}-annihilation-driven jet, thereby comfortably satisfying constraints on event rate and apparent luminosity. We also assess magnetic mechanisms to transform the available energy into a GRB. If the central object does not collapse immediately into a black hole, it will be convective and it is expected to act as an effective large scale dynamo, amplifying the seed magnetic fields to a few times 1017 G within a small fraction of a second. The associated spindown time-scale is 0.2 s, coinciding with the typical duration of a short GRB. The efficiencies of the various assessed magnetic processes are high enough to produce isotropized luminosities in excess of 1052 erg/s even without beaming.
Abstract Copyright:
2003 RAS
Journal keyword(s):
dense matter - hydrodynamics - neutrinos - methods: numerical - stars: neutron - gamma-rays: bursts
Simbad objects:
6
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