研究成果・発表論文

Systematic two-dimensional radiation-hydrodynamic simulations of super-Eddington accretion flow and outflow: Comparison with the slim disk model

Kitaki, Takaaki,   Mineshige, Shin,   Ohsuga, Ken,   & Kawashima, Tomohisa


要旨
To what extent can the one-dimensional slim disk model reproduce the multi-dimensional results of global radiation-hydrodynamic simulations of super-Eddington accretion? With this question in mind, we perform a systematic simulation study of accretion flow onto a non-spinning black hole for a variety of black hole masses of (10-10$^7$) M$_☉$ and mass accretion rates of (1.4 × 10$^2$-5.6 × 10$^3$) L$_Edd$/c$^2$ (with L$_Edd$ and c being the Eddington luminosity and the speed of light). In order to adequately resolve large-scale outflow structure, we extensively expand a simulation box to cover the space of 3000 r$_S$ (with r$_S$ being the Schwarzschild radius), larger than those in most previous studies, so that we can put relatively large angular momentum on the gas injected from the outer simulation boundary. The adopted Keplerian radius, at which the centrifugal force balances the gravitational force, is r$_K$ = 300 r$_S$. The injected mass first falls and is accumulated at around this radius and then slowly accretes toward the central black hole via viscosity. We simulate such accretion processes, taking inverse and bulk Compton scattering into account. The simulated accretion flow is in a quasi-steady state inside r$_qss$ ̃ 200 r$_S$. Within this radius the flow properties are, on the whole, in good agreement with those described by the slim disk model except that the radial density profile of the underlying disk is much flatter, \ensuremathh̊o \ensuremath∝ r$^-0.73$ (cf. \ensuremath\o̊ \ensuremath∝ r$^-3/2$ in the slim disk model), due probably to efficient convection. We find very weak outflow from inside r ̃ 200 r$_S$, unlike the previous studies.




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