Black-Hole Accretion Discs and Jets at Super-Eddington Luminosity

Abstract

Super-Eddington accretion discs with 3 and 15 dot M_E around black holes with mass 10 M_sun are examined by two-dimensional radiation hydrodynamical calculations extending from the inner disc edge to 5*10^4 r_g and lasting up to \sim 10^6 r_g/c. The dominant radiation-pressure force in the inner region of the disc accelerates the gas vertically to the disc plane, and jets with 0.2 -- 0.4$c$ are formed along the rotational axis. In the case of the lower accretion rate, the initially anisotropic high-velocity jet expands outward and becomes gradually isotropic flow in the distant region. The mass-outflow rate from the outer boundary is as large as \sim 10^{19} -- 10^{23} g s^{-1}, but it is variable and intermittent with time; that is, the outflow switches occasionally to inflow in the distant region. The luminosity also varies as \sim 10^{40} -- 10^{42} erg s^{-1} on a long time-scale. On the other hand, the jet in the case of the higher accretion rate maintains its initial anisotropic shape even after it goes far away. The mass-outflow rate and the luminosity attain to steady values of 3*10^{19} g s^{-1} and 1.3*10^{40} erg s^{-1}, respectively. In accordance with the local analysis of the slim accretion disc model, the disc is thermally unstable in the case of 3 \dot M_E} but stable in the case of 15 \dot M_E. The super-Eddington model with 15 \dot M_E is promising to explain a small collimation degree of the jet and a large mass-outflow rate observed in the X-ray source SS 433.