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Accretion into Black Hole, and Formation of Magnetically Arrested Accretion Disks

1
Space Research Institute of Russian Academy of Sciences, Profsoyuznaya 84/32, 117997 Moscow, Russia
2
National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Kashirskoe Shosse 31, 115409 Moscow, Russia
3
Moscow Institute of Physics and Technology MIPT, Institutskiy Pereulok, 9, Dolgoprudny, 141701 Moscow, Russia
Universe 2019, 5(6), 146; https://doi.org/10.3390/universe5060146
Received: 28 March 2019 / Revised: 29 May 2019 / Accepted: 31 May 2019 / Published: 11 June 2019
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Abstract

The exact time-dependent solution is obtained for a magnetic field growth during a spherically symmetric accretion into a black hole (BH) with a Schwarzschild metric. Magnetic field is increasing with time, changing from the initially uniform into a quasi-radial field. Equipartition between magnetic and kinetic energies in the falling gas is supposed to be established in the developed stages of the flow. Estimates of the synchrotron radiation intensity are presented for the stationary flow. The main part of the radiation is formed in the relativistic region r 7 r g , where r g is a BH gravitational radius. The two-dimensional stationary self-similar magnetohydrodynamic solution is obtained for the matter accretion into BH, in a presence of a large-scale magnetic field, under assumption, that the magnetic field far from the BH is homogeneous and its influence on the flow is negligible. At the symmetry plane perpendicular to the direction of the distant magnetic field, the dense quasi-stationary disk is formed around BH, which structure is determined by dissipation processes. Solutions of the disk structure have been obtained for a laminar disk with Coulomb resistivity and for a turbulent disk. Parameters of the shock forming due to matter infall onto the disk are obtained. The radiation spectrum of the disk and the shock are obtained for the 10 M BH. The luminosity of such object is about the solar one, for a characteristic galactic gas density, with possibility of observation at distances less than 1 kpc. The spectra of a laminar and a turbulent disk structure around BH are very different. The laminar disk radiates mainly in the ultraviolet, the turbulent disk emits a large part of its flux in the infrared. It may occur that some of the galactic infrared star-like sources are a single BH in the turbulent accretion state. The radiative efficiency of the magnetized disk is very high, reaching 0.5 M ˙ c 2 . This model of accretion was called recently as a magnetically arrested disk (MAD). Numerical simulations of MAD and its appearance during accretion into neutron stars, are considered and discussed. View Full-Text
Keywords: accretion disk; black holes; magnetic field accretion disk; black holes; magnetic field
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Bisnovatyi-Kogan, G.S. Accretion into Black Hole, and Formation of Magnetically Arrested Accretion Disks. Universe 2019, 5, 146.

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