Global 3D Radiation Magnetohydrodynamic Simulations of Accretion onto a Stellar-mass Black Hole at Sub- and Near-critical Accretion Rates

We present global 3D radiation magnetohydrodynamic simulations of accretion onto a 6.62 solar-mass black hole, with quasi-steady-state accretion rates reaching 0.016-0.9 times the critical accretion rate, which is defined as the accretion rate for powering the Eddington luminosity, assuming a 10% radiative efficiency, in three different runs. The simulations show no sign of thermal instability over hundreds of thermal timescales at 10 r (g). The energy dissipation occurs close to the mid-plane in the near-critical runs and near the disk surface in the low-accretion rate run. The total radiative luminosity inside similar to 20 r (g) is about 1%-30% of the Eddington limit, with radiative efficiencies of about 6% and 3%, respectively, in the sub- and near-critical accretion regimes. In both cases, self-consistent turbulence generated by the magnetorotational instability leads to angular momentum transfer, and the disk is supported by magnetic pressure. Outflows from the central low-density funnel, with a terminal velocity of similar to 0.1c, are seen only in the near-critical runs. We conclude that these magnetic pressure-dominated disks are thermally stable and thicker than the alpha disk, and that the effective temperature profiles are much flatter than those in the alpha disks. The magnetic pressures of these disks are comparable within an order of magnitude to the previous analytical magnetic pressure-dominated disk model.