The Radiative Efficiency and Spectra of Slowly Accreting Black Holes from Twoerature GRRMHD Simulations

Benjamin R. Ryan, Sean M. Ressler, Joshua C. Dolence, Alexander Tchekhovskoy, Charles Gammie, Eliot Quataert

Research output: Contribution to journalArticlepeer-review


We present axisymmetric numerical simulations of radiatively inefficient accretion flows onto black holes combining general relativity, magnetohydrodynamics, self-consistent electron thermodynamics, and frequencydependent radiation transport. We investigate a range of accretion rates up to 10-5 MEdd onto a 108 Mblack hole with spin a = 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 M to inverse-Compton-dominated at our highest M. In contrast to canonical analytic models, we find that by M M 10-5 Edd, the flow approaches ~1% radiative efficiency, with much of the radiation due to inverseCompton scattering off Coulomb-heated electrons far from the black hole. These results have broad implications for modeling of accreting black holes across a large fraction of the accretion rates realized in observed systems.

Original languageEnglish (US)
Article numberL24
JournalAstrophysical Journal Letters
Issue number2
StatePublished - Aug 1 2017


  • accretion, accretion disks
  • black hole physics
  • magnetohydrodynamics (MHD)
  • methods: numerical
  • radiation: dynamics

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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