The Radiative Efficiency and Spectra of Slowly Accreting Black Holes from Two-temperature GRRMHD Simulations

Journal Article · Mon Jul 31 00:00:00 EDT 2017 · The Astrophysical Journal. Letters (Online)

DOI:https://doi.org/10.3847/2041-8213/aa8034· OSTI ID:1415406

Ryan, Benjamin R. ^[1]; Ressler, Sean M. ^[2]; Dolence, Joshua C. ^[3]; Tchekhovskoy, Alexander ^[4]; Gammie, Charles ^[5]; Quataert, Eliot ^[2]

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1. Univ. of Illinois, Urbana, IL (United States). Dept. of Astronomy
2. Univ. of California, Berkeley, CA (United States). Dept. of Astronomy. Dept. of Physics. Theoretical Astrophysics Center
3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
4. Univ. of California, Berkeley, CA (United States). Dept. of Astronomy. Dept. of Physics. Theoretical Astrophysics Center; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Northwestern Univ., Evanston, IL (United States). Center for Interdisciplinary Exploration & Research in Astrophysics (CIERA), Physics & Astronomy
5. Univ. of Illinois, Urbana, IL (United States). Dept. of Astronomy. Dept. of Physics

In this paper, we present axisymmetric numerical simulations of radiatively inefficient accretion flows onto black holes combining general relativity, magnetohydrodynamics, self-consistent electron thermodynamics, and frequency-dependent radiation transport. We investigate a range of accretion rates up to $${10}^{-5}\,{\dot{M}}_{\mathrm{Edd}}$$ onto a $${10}^{8}\,{M}_{\odot }$$ black hole with spin $${a}_{\star }=0.5$$. We report on averaged flow thermodynamics as a function of accretion rate. We present the spectra of outgoing radiation and find that it varies strongly with accretion rate, from synchrotron-dominated in the radio at low $$\dot{M}$$ to inverse-Compton-dominated at our highest $$\dot{M}$$. In contrast to canonical analytic models, we find that by $$\dot{M}\approx {10}^{-5}\,{\dot{M}}_{\mathrm{Edd}}$$, the flow approaches $$\sim 1 \% $$ radiative efficiency, with much of the radiation due to inverse-Compton scattering off Coulomb-heated electrons far from the black hole. Finally, these results have broad implications for modeling of accreting black holes across a large fraction of the accretion rates realized in observed systems.

• Research Organization: Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of California, Berkeley, CA (United States); Univ. of Illinois, Urbana, IL (United States)
• Sponsoring Organization: LANL Laboratory Directed Research and Development (LDRD) Program; National Aeronautics and Space Administration (NASA) (United States); National Science Foundation (NSF) (United States); USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC52-06NA25396
• OSTI ID: 1415406
• Report Number(s): LA-UR--17-25079
• Journal Information: The Astrophysical Journal. Letters (Online), Journal Name: The Astrophysical Journal. Letters (Online) Journal Issue: 2 Vol. 844; ISSN 2041-8213
• Publisher: Institute of Physics (IOP)
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
accretion disks
black hole physics
magnetohydrodynamics (MHD)
numerical methods
radiation dynamics