A global threedimensional radiation magnetohydrodynamic simulation of supereddington accretion disks
Abstract
We study superEddington accretion flows onto black holes using a global threedimensional radiation magnetohydrodynamical simulation. We solve the timedependent radiative transfer equation for the specific intensities to accurately calculate the angular distribution of the emitted radiation. Turbulence generated by the magnetorotational instability provides selfconsistent angular momentum transfer. The simulation reaches inflow equilibrium with an accretion rate ∼220 L {sub Edd}/c {sup 2} and forms a radiationdriven outflow along the rotation axis. The mechanical energy flux carried by the outflow is ∼20% of the radiative energy flux. The total mass flux lost in the outflow is about 29% of the net accretion rate. The radiative luminosity of this flow is ∼10 L {sub Edd}. This yields a radiative efficiency ∼4.5%, which is comparable to the value in a standard thin disk model. In our simulation, vertical advection of radiation caused by magnetic buoyancy transports energy faster than photon diffusion, allowing a significant fraction of the photons to escape from the surface of the disk before being advected into the black hole. We contrast our results with the lower radiative efficiencies inferred in most models, such as the slim disk model, which neglect vertical advection. Our inferred radiative efficiencies also exceed publishedmore »
 Authors:
 HarvardSmithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
 Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)
 Canadian Institute for Theoretical Astrophysics. Toronto, ON M5S3H4 (Canada)
 Publication Date:
 OSTI Identifier:
 22370149
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Astrophysical Journal; Journal Volume: 796; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; ANGULAR DISTRIBUTION; ANGULAR MOMENTUM TRANSFER; BLACK HOLES; COMPUTERIZED SIMULATION; DIFFUSION; EMISSION; EQUILIBRIUM; INSTABILITY; LUMINOSITY; MAGNETOHYDRODYNAMICS; POWER TRANSMISSION; RADIANT HEAT TRANSFER; ROTATION; SPECTRA; SURFACES; TIME DEPENDENCE; TURBULENCE; UNIVERSE; XRAY SOURCES
Citation Formats
Jiang, YanFei, Stone, James M., and Davis, Shane W. A global threedimensional radiation magnetohydrodynamic simulation of supereddington accretion disks. United States: N. p., 2014.
Web. doi:10.1088/0004637X/796/2/106.
Jiang, YanFei, Stone, James M., & Davis, Shane W. A global threedimensional radiation magnetohydrodynamic simulation of supereddington accretion disks. United States. doi:10.1088/0004637X/796/2/106.
Jiang, YanFei, Stone, James M., and Davis, Shane W. 2014.
"A global threedimensional radiation magnetohydrodynamic simulation of supereddington accretion disks". United States.
doi:10.1088/0004637X/796/2/106.
@article{osti_22370149,
title = {A global threedimensional radiation magnetohydrodynamic simulation of supereddington accretion disks},
author = {Jiang, YanFei and Stone, James M. and Davis, Shane W.},
abstractNote = {We study superEddington accretion flows onto black holes using a global threedimensional radiation magnetohydrodynamical simulation. We solve the timedependent radiative transfer equation for the specific intensities to accurately calculate the angular distribution of the emitted radiation. Turbulence generated by the magnetorotational instability provides selfconsistent angular momentum transfer. The simulation reaches inflow equilibrium with an accretion rate ∼220 L {sub Edd}/c {sup 2} and forms a radiationdriven outflow along the rotation axis. The mechanical energy flux carried by the outflow is ∼20% of the radiative energy flux. The total mass flux lost in the outflow is about 29% of the net accretion rate. The radiative luminosity of this flow is ∼10 L {sub Edd}. This yields a radiative efficiency ∼4.5%, which is comparable to the value in a standard thin disk model. In our simulation, vertical advection of radiation caused by magnetic buoyancy transports energy faster than photon diffusion, allowing a significant fraction of the photons to escape from the surface of the disk before being advected into the black hole. We contrast our results with the lower radiative efficiencies inferred in most models, such as the slim disk model, which neglect vertical advection. Our inferred radiative efficiencies also exceed published results from previous global numerical simulations, which did not attribute a significant role to vertical advection. We briefly discuss the implications for the growth of supermassive black holes in the early universe and describe how these results provided a basis for explaining the spectrum and population statistics of ultraluminous Xray sources.},
doi = {10.1088/0004637X/796/2/106},
journal = {Astrophysical Journal},
number = 2,
volume = 796,
place = {United States},
year = 2014,
month =
}

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GLOBAL STRUCTURE OF THREE DISTINCT ACCRETION FLOWS AND OUTFLOWS AROUND BLACK HOLES FROM TWODIMENSIONAL RADIATIONMAGNETOHYDRODYNAMIC SIMULATIONS
We present the detailed global structure of black hole accretion flows and outflows through newly performed twodimensional radiationmagnetohydrodynamic simulations. By starting from a torus threaded with weak toroidal magnetic fields and by controlling the central density of the initial torus, {rho}{sub 0}, we can reproduce three distinct modes of accretion flow. In model A, which has the highest central density, an optically and geometrically thick supercritical accretion disk is created. The radiation force greatly exceeds the gravity above the disk surface, thereby driving a strong outflow (or jet). Because of mild beaming, the apparent (isotropic) photon luminosity is {approx}22L{sub E}more »