Self-consistent models of spherical accretion onto black holes. I. One-temperature solutions

Spherically symmetric, steady state accretion onto a black hole is considered for various dimensionless accretion rates (m) over dot (=(M) over dot c(2)/L-E, where (M) over dot is the accretion rate and L-E is the Eddington luminosity). Models are constructed by iteratively integrating relativistic hydrodynamic and radiation moment equations with bremsstrahlung and Comptonization as the main radiative processes. Electrons and ions are assumed to be coupled completely. The effects of preheating, and the shock that may result, are also considered. At least one type of self-consistent model is found for any (m) over dot, self-consistency meaning that the gas at all radii is heated by the radiation it produces. Two sets of models (characterized by different temperatures) were found in the range 3 less than or similar to (m) over dot less than or similar to 100. The dimensionless luminosity l (=L/L-E) is 5.8 x 10(-5) (m) over dot(2) for (m) over dot << 1. Low temperature models (T similar or equal to 10(4) K), which exist for (m) over dot greater than or similar to 0.1, have l similar to 7 x 10(-10) (m) over dot ln(10(8)/(m) over dot); high-temperature models, which exist for 3 less than or similar to (m) over dot less than or similar to 100, have 3 x 10(-4) less than or similar to l less than or similar to 3 x 10(-2). The (m) over dot = 100 model has the highest luminosity of all: l = 2.6 x 10(-2). High-(m) over dot models have correct mean photon energies for AGNs. Because of the effects of preheating, no steady state high-temperature self-consistent solution exists for 0.1 less than or similar to (m) over dot less than or similar to 3 without a shock, and none exists for (m) over dot greater than or similar to 100 regardless of the presence or absence of a shock. The calculations also suggest that the high-temperature (m) over dot > 1 model is unstable at a fixed accretion rate.