Radiative shocks in disk accretion

Radiative shock waves standing in disk accretion flows are examined under the equilibrium diffusion approximation (1T limit) in the optically thick case, taking into account the hydrostatic equilibrium in the vertical direction. In contrast to the usual one-dimensional shock, where the gas density of the post-shock region increases due to the shock compression, if the shock is sufficiently strong, the gas density in the post-shock region often decreases due to the vertical expansion behind the shock front. However, the surface density behaves like the gas density in the usual shocks, and increases up to 7 in the radiation pressure dominated shock. Hence, the vertical optical depth in the post-shock region rises, in spite of the reduction of the gas density. In addition, similar to the usual radiative shock, there appears a radiative precursor in the pre-shock region before the shock front, due to the radiative diffusion effect. We derive the overall jump conditions for the radiative shock in disk accretion flows, and solve the structure of the radiative precursor for both the gas and radiation pressure dominated cases. The solutions are quite fundamental in disk-accretion shock problems, and should be developed in various aspects.