Radiative Flow in a Luminous Disk

Radiatively-driven flow in a luminous disk is examined in the subrelativisticregime of $(v/c)^1$, taking account of radiation transfer. The flow is assumedto be vertical, and the gravity and gas pressure are ignored. When internalheating is dropped, for a given optical depth and radiation pressure at theflow base (disk ``inside''), where the flow speed is zero, the flow isanalytically solved under the appropriate boundary condition at the flow top(disk ``surface''), where the optical depth is zero. The loaded mass andterminal speed of the flow are both determined by the initial conditions; themass-loss rate increases as the initial radiation pressure increases, while theflow terminal speed increases as the initial radiation pressure and the loadedmass decrease. In particular, when heating is ignored, the radiative flux $F$is constant, and the radiation pressure $P_0$ at the flow base with opticaldepth $\tau_0$ is bound in the range of $2/3 < cP_0/F < 2/3 + \tau_0$. In thiscase, in the limit of $cP_0/F = 2/3 + \tau_0$, the loaded mass diverges and theflow terminal speed becomes zero, while, in the limit of $cP_0/F = 2/3$, theloaded mass becomes zero and the terminal speed approaches $(3/8)c$, which isthe terminal speed above the luminous flat disk under an approximation of theorder of $(v/c)^1$. We also examine the case where heating exists, and findthat the flow properties are qualitatively similar to the case without heating.Comment: 7 pages, 4 figure