A Binary Neutron Star GRB Model

In this paper we present the preliminary results of a model for the production of gamma-ray bursts (GRBs) through the compressional heating of binary neutron stars near their last stable orbit prior to merger. Recent numerical studies of the general relativistic (GR) hydrodynamics in three spatial dimensions of close neutron star binaries (NSBs) have uncovered evidence for the compression and heating of the individual neutron stars (NSs) prior to merger [1,2]. This effect will have significant effect on the production of gravitational waves, neutrinos and, ultimately, energetic photons. The study of the production of these photons in close NSBs and, in particular, its correspondence to observed GRBs is the subject of this paper. The gamma-rays arise as follows. Compressional heating causes the neutron stars to emit neutrino pairs which, in turn, annihilate to produce a hot electron-positron pair plasma. This pair-photon plasma expands rapidly until it becomes optically thin, at which point the photons are released. We show that this process can indeed satisfy three basic requirements of a model for cosmological gamma-ray bursts: 1) sufficient gamma-ray energy release (> 10 ergs) to produce observed fluxes, 2) a time-scale of the primary burst duration consistent with that of a “classical” GRB (∼ 10 seconds), 3) peak of photon number spectrum matches that of “classical” GRB (∼ 300 keV). NEUTRON STAR HEATING The method for solving the general relativistic field equations in three spatial dimensions has been discussed in [1,2]. At each time slice we obtain an exact (to numerical accuracy) instantaneous solution to the GR field equations. The hydrodynamic equations are then evolved for the moving matter against these GR fields. This method ignores gravitational waves, however in [1] it was shown that the effect is very small; J̇ ωJ ∼ 10, where J is the angular momentum and ω is the angular frequency of the NSB. The computational evolution calculation of NSBs and their GR fields begins by generating two identical non-spinning neutron stars with an initial mass and an EOS. The stars are allowed to evolve until a stationary orbit is achieved with a