Black hole accretion discs and jets at super-Eddington luminosity

Abstract

Super-Eddington accretion discs with 3̇ME and 15̇M E around black holes with mass 10M⊙ 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 occasionally 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 3̇M E but stable in the case of 15̇ME. The super-Eddington model with 15̇ME promises to explain the small collimation degree of the jet and the large mass-outflow rate observed in the X-ray source SS 433.