Black hole accretion discs and jets at super-Eddington luminosity

Abstract

Super-Eddington accretion discs with 3M ̇ E and 15M ̇ E around black holes with mass 10 M⊙ are examined by two-dimensional radiation hydrodynamical calculations extending from the inner disc edge to 5 × 104rg and lasting up to ∼106 rg/c. The dominant radiation pressure force in the inner region of the disc accelerates the gas vertically to the disc plane, and jets with 0.2–0.4c 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 ∼1019 –1023 g s−1, but it is variable and intermittent with time; that is, the outflow switches occa- sionally to inflow in the distant region. The luminosity also varies as ∼1040–1042 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 steady values of 3 × 1019 g s−1 and 1.3 × 1040 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 3M ̇ E but stable in the case of 15M ̇ E. The super-Eddington model with 15M ̇ E promises to explain the small collimation degree of the jet and the large mass-outflow rate observed in the X-ray source SS 433.