@article{12593,
  author = {Jason Dexter and Nicolas Scepi and Mitchell Begelman},
  title = {Radiation GRMHD Simulations of the Hard State of Black Hole X-ray Binaries and the Collapse of a Hot Accretion Flow},
  abstract = {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/LEdd≳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/LEdd∼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.},
  year = {2021},
  journal = {The Astrophysical Journal Letters},
  volume = {919},
  pages = {L20},
  month = {2021-09},
  url = {https://iopscience.iop.org/article/10.3847/2041-8213/ac2608},
  doi = {10.3847/2041-8213/ac2608},
}