Hot one-temperature accretion flows around black holes

We describe hot, optically-thin solutions for one-temperature accretion disks around black holes. We include cooling by synchrotron, bremsstrahlung, and Comptonization. Our solutions are thermally and viscously stable, with gas temperatures on the order of T \sim 10^9-10^{10.7}K. The thermal stability is a direct result of the inclusion of synchrotron cooling. The new solution branch is related to the advection-dominated solution for a two-temperature gas described by Narayan \& Yi (1995b). It is present only for mass accretion rates less than some critical \dot{M}_{crit} which depends on the radius R and viscosity parameter \alpha. The solutions are advection-dominated for extremely low values of \dot{M}. However, for a range of intermediate accretion rates, the new solutions are both hot (T \sim 10^{10}K) and cooling-dominated. Because of this new feature, one-temperature solutions are significantly more luminous than the corresponding two temperature solutions. The radial profile of the new solutions is unusual. The inner parts of the flow are cooling-dominated and have a disk-like geometry, while the outer parts are fully advection-dominated and nearly quasi-spherical