hero – A 3D general relativistic radiative post-processor for accretion discs around black holes

Mon. Not. R. Astron. Soc.

Zhu

Psaltis

et al. 2016

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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.

Section: Gravitational Redshiftmentioning

confidence: 64%

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

Mon. Not. R. Astron. Soc.

Zhu

Psaltis

et al. 2016

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“…We produced spectra, images, and lightcurves from our simulations using two post-processing codes. For computing full spectra, we used HEROIC, (Zhu et al 2015;Narayan et al 2016), a code that solves for the spectrum and angular distribution of radiation at each grid position self-consistently. Inverse Compton scattering is included along with free-free (from both e − e and e − i interactions) and synchrotron emission and absorption.…”

Section: Radiative Transfermentioning

confidence: 99%

Two-temperature, Magnetically Arrested Disc simulations of the jet from the supermassive black hole in M87

Chael

Monthly Notices of the Royal Astronomical Society

Johnson

2019

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151

163

We present two-temperature, radiative general relativistic magnetohydrodynamic simulations of Magnetically Arrested Discs (MAD) that launch powerful relativistic jets. The mass accretion rates of our simulations are scaled to match the luminosity of the accretion flow around the supermassive black hole in M87. We consider two sub-grid prescriptions for electron heating: one based on a Landau-damped turbulent cascade, and the other based on heating from trans-relativistic magnetic reconnection. The simulations produce jets with power on the order of the observed value for M87. Both simulations produce spectra that are consistent with observations of M87 in the radio, millimetre, and submillimetre. Furthermore, the predicted image core-shifts in both models at frequencies between 15 GHz and 86 GHz are consistent with observations. At 43 and 86 GHz, both simulations produce wide opening angle jets consistent with VLBI images. Both models produce 230 GHz images with distinct black hole shadows that are resolvable by the Event Horizon Telescope (EHT), although at a viewing angle of 17 • , the 230 GHz images are too large to match EHT observations from 2009 and 2012. The 230 GHz images from the simulations are dynamic on time-scales of months to years, suggesting that repeated EHT observations may be able to detect the motion of rotating magnetic fields at the event horizon.

“…Therefore, in principle, it may be sufficient to stop after doing short characteristics, at least if we are interested only in the radiation field at small radii. The differences are more noticeable at larger radii because of the presence of ray defects in the short characteristic solution (see Zhu et al 2015).…”

Section: Radiation Post-processing With Heroicmentioning

confidence: 99%

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

Monthly Notices of the Royal Astronomical Society

Sądowski

Soria

2017

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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.