Theory and astrophysical consequences of a magnetized torus around a rapidly rotating black hole

We analyze the topology, lifetime, and emissions of a torus around a black hole formed in hypernovae and black hole-neutron star coalescence. The torus is ab initio uniformly magnetized, represented by two counter oriented current-rings, and develops a state of suspended accretion against a “magnetic wall” around the black hole. Magnetic stability of the torus gives rise to a new fundamental limit EB/Ek < 0.1 for the ratio of poloidal magnetic field energy-to-kinetic energy, corresponding to a maximum magnetic field strength Bc ' 10G (7M /MH) (6MH/R) (MT /0.03MH). The lifetime of rapid spin of the black hole is effectively defined by the timescale of dissipation of black hole-spin energy Erot in the horizon, and satisfies T ' 40s(MH/7M )(R/6MH)(0.03MH/MT ) for a black hole of mass MH surrounded by a torus of mass MT and radius R. Erot of the black hole. The torus converts a major fraction Egw/Erot ∼ 10% into gravitational radiation through a finite number of multipole mass-moments, and a smaller fraction into MeV neutrinos and baryon-rich winds. At a source distance of 100Mpc, these emissions over N = 2 × 10 periods give rise to a characteristic strain amplitude √ Nhchar ' 6 × 10−21. We argue that torus winds create an open magnetic flux-tube on the black hole, which carries a minor fraction Ej/Erot ' 10−3 in baryon-poor outflows to infinity. We conjecture that these are not high-sigma outflows owing, in part, to magnetic reconnection in surrounding current sheets. The fraction Ej/Erot ∼ (1/4)(MH/R) is standard for a universal horizon halfopening angle θH ' MH/R of the open flux-tube. We identify this baryon poor output of tens of seconds with GRBs with contemporaneous and strongly correlated emissions in gravitational radiation, conceivably at multiple frequencies. Ultimately, this leaves a black hole binary surrounded by a supernova remnant.