Self-consistent models of spherical accretion onto black holes. II. Two-temperature solutions with pairs

Two-temperature spherical accretion onto a black hole is considered with the effect of thermal pair production. Leptons (electrons and positrons) are coupled with ions by Coulomb interactions. Relativistic hydrodynamic and radiation moment equations are iteratively solved. Relativistic bremsstrahlung and Comptonization are the main radiative processes, and the preheating and shock are also considered. Self-consistent models are found in the range, ṁ ≲ 0.1 and 5 ≤ ṁ ≤ 30, where ṁ ≡ Ṁc²/L_E with M being the mass accretion rate. Between 0.1 ≲ ṁ ≲ 5, no self-consistent steady state solution exist due to the Compton preheating. When ṁ ≳ 30, ions and leptons are completely coupled by Coulomb interaction, and the flow is one temperature. When ṁ ≳ 0.1, these self-consistent models have ≃2 times smaller luminosity than the corresponding (same ṁ) one-temperature model. However, when 5 ≤ ṁ ≤ 30, they have higher luminosity, up to 1.5 times. Pairs produced in these models are always less than 10^-1.5 of ionized electrons. A different higher luminosity, pair-abundant branch of solutions are also found: they have ≃10 times the luminosity of the pair-deficient solutions. For these the pair density is roughly equal to the normal electron density.