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2003ApJ...584..937V -
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Astrophys. J., 584, 937-953 (2003/February-3)
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Theory and astrophysical consequences of a magnetized torus around a rapidly rotating black hole.
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VAN PUTTEN M.H.P.M. and LEVINSON A.
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Abstract (from CDS):
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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 counteroriented 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 E_B_/E_{k}<0.1 for the ratio of poloidal magnetic field energy to kinetic energy, corresponding to a maximum magnetic field strength B_{c}≃10^{16}G7M_{☉}/M_{H}6M_{H}/R^{2}M_{T}/0.03M_{H}^{1/2}. The lifetime of rapid spin of the black hole, effectively defined by the timescale of dissipation of spin energy E_{rot}in the horizon, hereby satisfies T≃40s(M_{H}/7M_{☉})(R/6M_{H})^{4}(0.03M_{H}/M_{T}) for a black hole of mass M_{H}surrounded by a torus of mass M_{T}and radius *R*. The torus converts a major fraction E_{gw}/E_{rot}∼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 100 Mpc, these emissions over N=2x10^{4} periods give rise to a characteristic strain amplitude N^{1/2}h_{char}≃6x10^{–21}. We argue that torus winds create an open magnetic flux tube on the black hole, which carries a minor fraction E_{j}/E_{rot}≃10^{–3} in baryon-poor outflows to infinity. We conjecture that these are not high-σ outflows, owing, in part, to magnetic reconnection in surrounding current sheets. The fraction E_{j}/E_{rot}~(1)/(4)(M_{H}/R)^{4} is standard for a universal horizon half-opening angle θ_{H}≃M_{H}/R of the open flux tube. We identify this baryon-poor output of tens of seconds with gamma-ray bursts 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.

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Abstract Copyright:
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Journal keyword(s):
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Black Hole Physics - Gamma Rays: Bursts - Gravitational Waves
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Simbad objects:
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3

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2021.03.04-20:46:36

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