Radiation magnetohydrodynamics for black hole-torus system in full general relativity: A step toward physical simulation

A radiation-magnetohydrodynamic simulation for the black hole-torus system is per- formed in the framework of full general relativity for the first time. A truncated moment formalism is employed for a general relativistic neutrino radiation transport. Several systems in which the black hole mass is MBH =3o r 6M� , the black hole spin is zero, and the torus mass is ≈ 0.14-0.38Mare evolved as models of the remnant formed after the merger of binary neutron stars or black hole-neutron star binaries. The equation of state and micro- physics for the high-density and high-temperature matter are phenomenologically taken into account in a semi-quantitative manner. It is found that the temperature in the inner region of the torus reaches > 10 MeV which enhances a high luminosity of neutrinos ∼ 10 51 ergs/s for MBH =6 Mand ∼ 10 52 ergs/s for MBH =3 M� . It is shown that neutrinos are likely to be emitted primarily toward the outward direction in the vicinity of the rotational axis and their energy density may be high enough to launch a low-energy short gamma-ray burst via the neutrino-antineutrino pair-annihilation process with the total energy deposition ∼ 10 47 - 10 49 ergs. It is also shown in our model that for MBH =3 M� , the neutrino luminosity is larger than the electromagnetic luminosity while for MBH =6 M� , the neutrino luminosity is comparable to or slightly smaller than the electromagnetic luminosity. Subject Index: 420, 425