Relativistic fluid disks in orbit around Kerr black holes

Fishbone, L.G.; Moncrief, Vincent

doi:10.1086/154565

Cited by 397 publications

(341 citation statements)

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“…We use the conservative code HARM (Gammie, McKinney & Tóth 2003) as our background GRMHD solution. Our initial conditions for the total fluid are the Fishbone & Moncrief (1976) equilibrium torus solution (see Appendix D) with inner radius r in = 6r g and with the maximum density of the disc occurring at r max = 12r g . Note that here and throughout r and θ refer to the Boyer-Lindquist coordinates.…”

Section: Application To An Accreting Black Hole In 2d Grmhd Simulationsmentioning

confidence: 99%

Electron thermodynamics in GRMHD simulations of low-luminosity black hole accretion

Ressler

Tchekhovskoy

Quataert

et al. 2015

Mon. Not. R. Astron. Soc.

171

238

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Simple assumptions made regarding electron thermodynamics often limit the extent to which general relativistic magnetohydrodynamic (GRMHD) simulations can be applied to observations of low-luminosity accreting black holes. We present, implement, and test a model that self-consistently evolves an entropy equation for the electrons and takes into account the effects of spatially varying electron heating and relativistic anisotropic thermal conduction along magnetic field lines. We neglect the back-reaction of electron pressure on the dynamics of the accretion flow. Our model is appropriate for systems accreting at ≪ 10 −5 of the Eddington accretion rate, so radiative cooling by electrons can be neglected. It can be extended to higher accretion rates in the future by including electron cooling and proton-electron Coulomb collisions. We present a suite of tests showing that our method recovers the correct solution for electron heating under a range of circumstances, including strong shocks and driven turbulence. Our initial applications to axisymmetric simulations of accreting black holes show that (1) physically-motivated electron heating rates that depend on the local magnetic field strength yield electron temperature distributions significantly different from the constant electron to proton temperature ratios assumed in previous work, with higher electron temperatures concentrated in the coronal region between the disc and the jet; (2) electron thermal conduction significantly modifies the electron temperature in the inner regions of black hole accretion flows if the effective electron mean free path is larger than the local scale-height of the disc (at least for the initial conditions and magnetic field configurations we study). The methods developed in this work are important for producing more realistic predictions for the emission from accreting black holes such as Sagittarius A* and M87; these applications will be explored in future work.

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Section: Application To An Accreting Black Hole In 2d Grmhd Simulationsmentioning

confidence: 99%

Electron thermodynamics in GRMHD simulations of low-luminosity black hole accretion

Ressler

Tchekhovskoy

Quataert

et al. 2015

Mon. Not. R. Astron. Soc.

171

238

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“…Main details of the simulations used in the present paper are given in Table 1. A thicker torus in the model of Fishbone & Moncrief (1976) is also more extended in radial direction. As the result, it may become impossible to maintain the boundary condition at the outer boundary, and the simulation becomes unstable.…”

Section: Numerical Simulationsmentioning

confidence: 88%

“…The main goal of the simulation was to form a moderately thin disc (H/R ∼ 0.1) around a Kerr (a = 0.9) black hole and consider the motion of the matter inside the inner edge of the disc. As the initial conditions, an exact relativistic torus solution by Fishbone & Moncrief (1976), section IIIb, was used with small magnetic fields introduced that are subsequently amplified by MHD instabilities in the disc. Amplified magnetic fields lead to outward angular momentum transfer and consequently to accretion from the torus through a moderately thick disc formed during the first two thousand dynamical time-scales (GM/c 3 ) of the simulation.…”

Section: Numerical Simulationsmentioning

confidence: 99%

On the Eddington limit for relativistic accretion discs

Abolmasov¹,

Chashkina²

2015

Mon. Not. R. Astron. Soc.

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Standard accretion disc model relies upon several assumptions, the most important of which is geometrical thinness. Whenever this condition is violated, new physical effects become important such as radial energy advection and mass loss from the disc. These effects are important, for instance, for large mass accretion rates when the disc approaches its local Eddington limit. In this work, we study the upper limits for standard accretion disc approximation and find the corrections to the standard model that should be considered in any model aiming on reproducing the transition to super-Eddington accretion regime. First, we find that for thin accretion disc, taking into account relativistic corrections allows to increase the local Eddington limit by about a factor of two due to stronger gravity in General Relativity (GR). However, violation of the local Eddington limit also means large disc thickness. To consider consequently the disc thickness effects, one should make assumptions upon the twodimensional rotation law of the disc. For rotation frequency constant on cylinders r sin θ = const, vertical gravity becomes stronger with height on spheres of constant radius. On the other hand, effects of radial flux advection increase the flux density in the inner parts of the disc and lower the Eddington limit. In general, the effects connected to disc thickness tend to increase the local Eddington limit even more. The efficiency of accretion is however decreased by advection effects by about a factor of several.

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“…The initial mass distribution is an isentropic hydroequilibrium torus (Fishbone & Moncrief 1976;Gammie et al 2003) with the inner edge at r r 10 g = and pressure maximum at r r 100 g = .…”

Section: Grmhd Simulationmentioning

confidence: 99%

Jet Signatures in the Spectra of Accreting Black Holes

Riordan¹,

Pe’er²,

McKinney³

2016

ApJ

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Jets are observed as radio emission in active galactic nuclei and during the low/hard state in X-ray binaries (XRBs), but their contribution at higher frequencies has been uncertain. We study the dynamics of jets in XRBs using the general-relativistic magnetohydrodynamic code HARM. We calculate the high-energy spectra and variability properties using a general-relativistic radiative transport code based on grmonty. We find the following signatures of jet emission: (i) a significant γ-ray peak above ∼10 22 Hz, (ii) a break in the optical/UV spectrum, with a change from L 0 n ñ n to L n ñ n , followed by another break at higher frequencies where the spectrum roughly returns to L 0 n ñ n , and (iii) a pronounced synchrotron peak near or below ∼10 14 Hz indicates that a significant fraction of any observed X-ray emission originates in the jet. We investigate the variability during a large-scale magnetic field inversion in which the Blandford-Znajek (BZ) jet is quenched and a new transient hot reconnecting plasmoid is launched by the reconnecting field. The ratio of the γ-rays to X-rays changes from L L 1 X > g in the BZ jet to L L 1 X < g during the launching of the transient plasmoid.

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Relativistic fluid disks in orbit around Kerr black holes

Cited by 397 publications

References 0 publications

Electron thermodynamics in GRMHD simulations of low-luminosity black hole accretion

Electron thermodynamics in GRMHD simulations of low-luminosity black hole accretion

On the Eddington limit for relativistic accretion discs

Jet Signatures in the Spectra of Accreting Black Holes

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