Modified Slim-Disk Model Based on Radiation-Hydrodynamic Simulation Data: The Conflict Between Outflow and Photon Trapping

Photon trapping and outflow are two key physics associated with the supercritical accretion flow. We investigate the conflict between these two processes based on two-dimensional radiation-hydrodynamic (RHD) simulation data and construct a simplified (radially) one-dimensional model. Mass loss due to outflow, which is not considered in the slim-disk model, will reduce surface density of the flow, and if very significant, it will totally suppress photon trapping effects. If the photon trapping is very significant, conversely, outflow will be suppressed because radiation pressure force will be reduced. To see what actually occurs, we examine the RHD simulation data and evaluate the accretion rate and outflow rate as functions of radius. We find that the former monotonically decreases, while the latter increases, as the radius decreases. However, the former is kept constant at small radii, inside several Schwarzschild radii, since the outflow is suppressed by the photon trapping effects. To understand the conflict between the photon trapping and outflow in a simpler way, we model the radial distribution of the accretion rate from the simulation data and build up a new (radially) one-dimensional model, which is similar to the slim-disk model but incorporates the mass loss effects due to the outflow. We find that the surface density (and, hence, the optical depth) is much reduced even inside the trapping radius, compared with the case without outflow, whereas the effective temperature distribution hardly changes. That is, the emergent spectra do not sensitively depend on the amount of mass outflow. We conclude that the slim-disk approach is valid for interpreting observations, even if the outflow is taken into account.Comment: 15 pages, 5 figures, accepted for publication in PAS

Global Structure of Three Distinct Accretion Flows and Outflows around Black Holes from Two-Dimensional Radiation-Magnetohydrodynamic Simulations

With a two-dimensional global Radiationmagnetohydrodynamic (RMHD) code [1], we could reproduce three distinct inflow-outflow modes around black holes. Our three models correspond to the twodimensional RMHD version of the slim disk (supercritical flow), the standard disk, and the RIAF, all with substantial outflows (see Figure 1) [2]. We find the supercritical disk accretion flow, of which the photon luminosity exceeds the Eddington luminosity. The vertical component of the radiation force balances that of the gravity in the disk region but it largely exceeds the gravity above the disk. Our RMHD simulations reveal a new type of jet, i.e., the radiatively driven, magnetically collimated outflow, which might account for the jets of radio-loud NLS1s and microquasars [3,4]. The disk, th

Radiation hydrodynamics simulations of wide-angle outflows from super-critical accretion disks around black holes

By performing two-dimensional radiation hydrodynamics simulations with large computational domain of 5000 Schwarzschild radius, we revealed that wide-angle outflow is launched via the radiation force from the super-critical accretion flows around black holes. The angular size of the outflow, of which the radial velocity (v_r) is over the escape velocity (v_esc), increases with an increase of the distance from the black hole. As a result, the mass is blown away with speed of v_r > v_esc in all direction except for the very vicinity of the equatorial plane, theta=0-85^circ, where theta is the polar angle. The mass ejected from the outer boundary per unit time by the outflow is larger than the mass accretion rate onto the black hole, ~150L_Edd/c^2, where L_Edd and c are the Eddington luminosity and the speed of light. Kinetic power of such wide-angle high-velocity outflow is comparable to the photon luminosity and is a few times larger than the Eddington luminosity. This corresponds to ~10^39-10^40 erg/s for the stellar mass black holes. Our model consistent with the observations of shock excited bubbles observed in some ultra-luminous X-ray sources (ULXs), supporting a hypothesis that ULXs are powered by the super-critical accretion onto stellar mass black holes.Comment: 9 pages, 8 figures, accepted for publication in PAS