2021/09/13 by Jason Dexter, Nicolas Scepi, Mitchell C. Begelman · 1 citation
Physics and Astronomy · #astro-ph.HE
paper · pdf · doi:10.3847/2041-8213/ac2608
9 pages, 4 figures, ApJL in press
arxiv created 2021/09/13 · arxiv updated 2021/10/04
We present global radiation GRMHD simulations of strongly magnetized accretion onto a spinning, stellar mass black hole at sub-Eddington rates. Using a frequency-dependent Monte Carlo procedure for Compton scattering, we self-consistently evolve a two-temperature description of the ion-electron fluid and its radiation field. For an Eddington ratio L/L\rm Edd \gtrsim 10-3, the emergent spectrum forms an apparent power law shape from thermal Comptonization up to a cutoff at ≃ 100 keV, characteristic of that seen in the hard spectral states of black hole X-ray binary systems. At these luminosities, the radiative efficiency is high (≈ 24%) and results in a denser midplane region where magnetic fields are dynamically important. For L/L\rm Edd ∼ 10-2, our hot accretion flow appears to undergo thermal runaway and collapse. Our simulations demonstrate that hot accretion flows can be radiatively efficient and provide an estimate of their maximum luminosity.