Direct Calculation of the Radiative Efficiency of an Accretion Disk Around a Black Hole

Noble, Scott C.; Krolik, Julian H.; Hawley, John F.

doi:10.1088/0004-637x/692/1/411

Cited by 211 publications

(291 citation statements)

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“…These equations amount to conservation of baryon number density and conservation of stress-energy (see Noble et al (2009) for more details). Taken together, they can be written as…”

Section: Hydrodynamicsmentioning

confidence: 99%

Relativistic Dynamics and Mass Exchange in Binary Black Hole Mini-disks

Bowen

Campanelli

Krolik

et al. 2017

ApJ

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113

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We present the first exploration of gas dynamics in a relativistic binary black hole system in which an accretion disk (a "mini-disk") orbits each black hole. We focus on 2D hydrodynamical studies of comparable-mass, non-spinning systems. Relativistic effects alter the dynamics of gas in this environment in several ways. Because the gravitational potential between the two black holes becomes shallower than in the Newtonian regime, the mini-disks stretch toward the L1 point and the amount of gas passing back and forth between the mini-disks increases sharply with decreasing binary separation. This "sloshing" is quasi-periodically modulated at 2 and 2.75 times the binary orbital frequency, corresponding to timescales of hours to days for supermassive binary black holes. In addition, relativistic effects add an m = 1 component to the tidally-driven spiral waves in the disks that are purely m = 2 in Newtonian gravity; this component becomes dominant when the separation is ∼ < 100 gravitational radii. Both the sloshing and the spiral waves have the potential to create distinctive radiation features that may uniquely mark supermassive binary black holes in the relativistic regime.

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“…These equations amount to conservation of baryon number density and conservation of stress-energy (see Noble et al (2009) for more details). Taken together, they can be written as…”

Section: Hydrodynamicsmentioning

confidence: 99%

Relativistic Dynamics and Mass Exchange in Binary Black Hole Mini-disks

Bowen

Campanelli

Krolik

et al. 2017

ApJ

Self Cite

113

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“…See Beckwith et al (2008), Shafee et al (2008), and Noble et al (2009) for recent discussions of this issue.…”

Section: Implications For Spectral Hardening and Continuum Spin Estimmentioning

confidence: 99%

The Effects of Magnetic Fields and Inhomogeneities on Accretion Disk Spectra and Polarization

Davis

Blaes

Hirose

et al. 2009

ApJ

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We present the results of one-and three-dimensional radiative transfer calculations of polarized spectra emerging from snapshots of radiation magnetohydrodynamical simulations of the local vertical structure of black hole accretion disks. The simulations cover a wide range of physical regimes relevant for the high/soft state of black hole X-ray binaries. We constrain the uncertainties in theoretical spectral color correction factors due to the presence of magnetic support of the disk surface layers and strong density inhomogeneities. For the radiation-dominated simulation, magnetic support increases the color correction factor by about 10%, but this is largely compensated by a 10% softening due to inhomogeneities. We also compute the effects of inhomogeneities and Faraday rotation on the resulting polarization. Magnetic fields in the simulations are just strong enough to produce significant Faraday depolarization near the spectral peak of the radiation field. X-ray polarimetry may therefore be a valuable diagnostic of accretion disk magnetic fields, being able to directly test simulations of magnetorotational turbulence.

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“…Shafee et al (2008) recently simulated a thin disk around a Schwarzschild hole and suggested that the ISCO stress cuts off sharply when the disk is thin. On the other hand, Noble, Krolik, & Hawley (2009) find additional ISCO stress even for a relatively thin disk. They further considered the observational implications of the ISCO stress using simple emission and absorption models coupled with relativistic ray tracing.…”

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confidence: 84%

Numerical Simulations of MHD Accretion Disks

Hawley¹

2009

Proc. IAU

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Abstract. Numerical simulations play an increasingly important role in investigating accretion disks and associated phenomena such as jets. This paper provides a few examples of recent results that have been obtained with simulations, both local or global. Keywords. accretion, accretion disks, magnetohydrodynamics: MHDThe most energetic phenomena in the universe are systems powered by gravity through accretion, specifically accretion disks surrounding compact stars and black holes. Accretion theory has largely been based primarily on a one-dimensional time-steady model consisting an optically thick, vertically-thin, Keplerian disk with an unknown, parameterized internal stress. While analytic models of this type provide considerable insight, their limitations are now well-known, and the observational data demand moving beyond this standard. Numerical simulations provide another means for investigating accretion disks.The governing equations of accretion are those of compressible magnetohydrodynamics (MHD). Magnetic fields render a differentially rotating fluid unstable to the magnetorotational instability -MRI; Balbus & Hawley (1991) -and the resulting turbulence accounts for the internal stress that drives accretion. These processes have been studied using local "shearing box" simulations -Hawley, Gammie & Balbus (1995). The shearing box is a Cartesian domain representing a small piece of the disk, assumed to be rotating with the local disk angular velocity, Ω. The equations include differential rotation, Coriolis force and the tidal potential. Local simulations have shown how the MRI produces angular momentum transfer and the degree to which the MRI stress acts like a Shakura-Sunyaev "α viscosity," where τ rφ = αP (Balbus & Papaloizou (1999)). MRI-driven turbulence generates substantial local stress, typically with α ∼ 0.01. The orbital energy released by that stress is locally dissipated by the turbulence into heat in an eddy turnover time (Simon, Hawley, & Beckwith (2009)). Shearing box simulations that combine MHD with flux limited diffusion (Hirose, Krolik, & Blaes (2009)) find that while the stress is roughly proportional to the total pressure (including both gas and radiation), the stress determines the pressure, not other way around. Increases in the stress lead to stronger turbulence, more turbulent dissipation, and more heat. A consequence of this is that radiation pressure-supported accretion disks are thermally stable, in contrast to expectations based on assuming a strict α viscosity. Because of its fundamentally magnetic nature, the stress is directly proportional to the magnetic energy which is itself determined by the balance between MRI driving (at a range of scales) and turbulent dissipation. At the present time, however, we don't have a way to predict the magnetic field energy as a local function of the state of the disk.The recognition that MHD turbulence provides the stress in disks leads to new questions. For example, because magnetic stresses don't necessarily diminish in the plunging reg...

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Direct Calculation of the Radiative Efficiency of an Accretion Disk Around a Black Hole

Cited by 211 publications

References 50 publications

Relativistic Dynamics and Mass Exchange in Binary Black Hole Mini-disks

Relativistic Dynamics and Mass Exchange in Binary Black Hole Mini-disks

The Effects of Magnetic Fields and Inhomogeneities on Accretion Disk Spectra and Polarization

Numerical Simulations of MHD Accretion Disks

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