Optically thick accretion onto black holes

Abstract

Spherically symmetric, steady-state, optically thick accretion onto a nonrotating black hole with the mass of$\mathfrak{M} = \mathfrak{M}_ \odot$ is studied. The gas accreting onto the black hole is assumed to be a fully ionized hydrogen plasma withn ₀=10⁸ cm⁻³ andT ₀=10⁴ K far from the black hole, and a new approximate expression for the Eddington factor is introduced. The luminosity is estimated to beL=1.875×10³³ erg s⁻¹, which primarily arises from the optical surface (τ∼1) ofT∼10⁴ K. The accretion flow is characterized by τ∼1 and (v/c)τ∼10. In the optically thin region, the flow remains isothermal, and the increase of temperature occurs at τ∼1. The radiative equilibrium is strictly realized at (v/c)τ∼10.