Semi-implicit scheme for treating radiation under M1 closure in general relativistic conservative fluid dynamics codes

Sądowski, Aleksander; Narayan, Ramesh; Tchekhovskoy, Alexander; Zhu, Yucong

doi:10.1093/mnras/sts632

Cited by 177 publications

(283 citation statements)

References 78 publications

(114 reference statements)

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“…Equation (36) is more troublesome since the divergence operator is best handled in the lab (Boyer-Lindquist) frame and it is necessary to write the energy conservation equation of radiation in the latter frame. The time component of the energy-momentum conservation law for radiation takes the form (see Sadowski et al 2013; (…”

Section: Solving For the Temperaturesmentioning

confidence: 99%

heroic: 3D general relativistic radiative post-processor with comptonization for black hole accretion discs

Narayan

Zhu

Psaltis

et al. 2016

Mon. Not. R. Astron. Soc.

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We describe HEROIC, an upgraded version of the relativistic radiative postprocessor code HERO described in a previous paper, but which now Includes Comptonization. HEROIC models Comptonization via the Kompaneets equation, using a quadratic approximation for the source function in the short characteristics radiation solver. It employs a simple form of accelerated lambda iteration to handle regions of high scattering opacity. In addition to solving for the radiation field, HEROIC also solves for the gas temperature by applying the condition of radiative equilibrium. We present benchmarks and tests of the Comptonization module in HEROIC with simple 1D and 3D scattering problems. We also test the ability of the code to handle various relativistic effects using model atmospheres and accretion flows in a black hole space-time. We present two applications of HEROIC to general relativistic MHD simulations of accretion discs. One application is to a thin accretion disc around a black hole. We find that the gas below the photosphere in the multi-dimensional HEROIC solution is nearly isothermal, quite different from previous solutions based on 1D plane parallel atmospheres. The second application is to a geometrically thick radiation-dominated accretion disc accreting at 11 times the Eddington rate. The multi-dimensional HEROIC solution shows that, for observers who are on axis and look down the polar funnel, the isotropic equivalent luminosity could be more than ten times the Eddington limit, even though the spectrum might still look thermal and show no signs of relativistic beaming.

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Section: Solving For the Temperaturesmentioning

confidence: 99%

heroic: 3D general relativistic radiative post-processor with comptonization for black hole accretion discs

Narayan

Zhu

Psaltis

et al. 2016

Mon. Not. R. Astron. Soc.

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“…In this paper, we use one of these state-of-theart codes, KORAL (Sadowski et al 2013, to explore the super-Eddington accreting stellar-mass BH model of ULXs. We present a number of general relativistic radiation MHD simulations of accreting BHs, corresponding to a range of super-Eddington mass accretion rates, BH spins and magnetic field strengths.…”

Section: Introductionmentioning

confidence: 99%

Spectra of black hole accretion models of ultraluminous X-ray sources

Narayan

Sądowski

Soria

2017

Monthly Notices of the Royal Astronomical Society

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We present general relativistic radiation MHD simulations of super-Eddington accretion on a 10M black hole. We consider a range of mass accretion rates, black hole spins, and magnetic field configurations. We compute the spectra and images of the models as a function of viewing angle, and compare them with the observed properties of ultraluminous X-ray sources (ULXs). The models easily produce apparent luminosities in excess of 10 40 erg s −1 for pole-on observers. However, the angle-integrated radiative luminosities rarely exceed 2.5 × 10 39 erg s −1 even for mass accretion rates of tens of Eddington. The systems are thus radiatively inefficient, though they are energetically efficient when the energy output in winds and jets is also counted. The simulated models reproduce the main empirical types of spectra -disk-like, supersoft, soft, hard -observed in ULXs. The magnetic field configuration, whether MAD ("magnetically arrested disk") or SANE ("standard and normal evolution"), has a strong effect on the results. In SANE models, the X-ray spectral hardness is almost independent of accretion rate, but decreases steeply with increasing inclination. MAD models with non-spinning black holes produce significantly softer spectra at higher values ofṀ , even at low inclinations. MAD models with rapidly spinning black holes are quite different from all other models. They are radiatively efficient (efficiency factor ∼ 10 − 20%), super-efficient when the mechanical energy output is also included (70%), and produce hard blazar-like spectra. In all models, the emission shows strong geometrical beaming, which disagrees with the more isotropic illumination favoured by observations of ULX bubbles.

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“…A variety of different closures have been adopted, including the flux-limited diffusion (FLD) approximation (Levermore & Pomraning 1981;Turner & Stone 2001;Krumholz et al 2007;Zhang et al 2011;van der Holst et al 2011;Commerçon et al 2011) and more recently the M1 method (González et al 2007;Skinner & Ostriker 2013;Saadowski et al 2013;McKinney et al 2013). A variety of recent studies of the global dynamics of black hole accretion disks (Ohsuga & Mineshige 2011;Saadowski et al 2013;McKinney et al 2013) have used such approximate closures. However, it is far from clear that such closures will be accurate everywhere in the flow.…”

Section: Introductionmentioning

confidence: 99%

“…While GRMHD flows including radiation using FLD or the M1 closure have recently been reported (Fragile et al 2012;Saadowski et al 2013;McKinney et al 2013), developing algorithms based on the formal solution of the RT equation in general relativity (GR) is a formidable challenge. Instead, in this paper we describe an intermediate step.…”

Section: Introductionmentioning

confidence: 99%

An Algorithm for Radiation Magnetohydrodynamics Based on Solving the Time-Dependent Transfer Equation

Jiang¹,

Stone²,

Davis³

2014

ApJS

129

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We describe a new algorithm for solving the coupled frequency-integrated transfer equation and the equations of magnetohydrodynamics in the regime that light-crossing time is only marginally shorter than dynamical timescales. The transfer equation is solved in the mixed frame, including velocity-dependent source terms accurate to O(v/c). An operator split approach is used to compute the specific intensity along discrete rays, with upwind monotonic interpolation used along each ray to update the transport terms, and implicit methods used to compute the scattering and absorption source terms. Conservative differencing is used for the transport terms, which ensures the specific intensity (as well as energy and momentum) are conserved along each ray to round-off error. The use of implicit methods for the source terms ensures the method is stable even if the source terms are very stiff. To couple the solution of the transfer equation to the MHD algorithms in the Athena code, we perform direct quadrature of the specific intensity over angles to compute the energy and momentum source terms. We present the results of a variety of tests of the method, such as calculating the structure of a non-LTE atmosphere, an advective diffusion test, linear wave convergence tests, and the well-known shadow test. We use new semi-analytic solutions for radiation modified shocks to demonstrate the ability of our algorithm to capture the effects of an anisotropic radiation field accurately. Since the method uses explicit differencing of the spatial operators, it shows excellent weak scaling on parallel computers.

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Semi-implicit scheme for treating radiation under M1 closure in general relativistic conservative fluid dynamics codes

Cited by 177 publications

References 78 publications

heroic: 3D general relativistic radiative post-processor with comptonization for black hole accretion discs

heroic: 3D general relativistic radiative post-processor with comptonization for black hole accretion discs

Spectra of black hole accretion models of ultraluminous X-ray sources

An Algorithm for Radiation Magnetohydrodynamics Based on Solving the Time-Dependent Transfer Equation

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