Radiatively-driven flow in a luminous disk is examined in the subrelativistic regime of ( v / c ) ^ { 1 } , taking account of radiation transfer .
The flow is assumed to be vertical , and the gravity and gas pressure are ignored .
When internal heating is dropped , for a given optical depth and radiation pressure at the flow base ( disk “ inside ” ) , where the flow speed is zero , the flow is analytically solved under the appropriate boundary condition at the flow top ( disk “ surface ” ) , where the optical depth is zero .
The loaded mass and terminal speed of the flow are both determined by the initial conditions ; the mass-loss rate increases as the initial radiation pressure increases , while the flow terminal speed increases as the initial radiation pressure and the loaded mass decrease .
In particular , when heating is ignored , the radiative flux F is constant , and the radiation pressure P _ { 0 } at the flow base with optical depth \tau _ { 0 } is bound in the range of 2 / 3 < cP _ { 0 } / F < 2 / 3 + \tau _ { 0 } .
In this case , in the limit of cP _ { 0 } / F = 2 / 3 + \tau _ { 0 } , the loaded mass diverges and the flow terminal speed becomes zero , while , in the limit of cP _ { 0 } / F = 2 / 3 , the loaded mass becomes zero and the terminal speed approaches ( 3 / 8 ) c , which is the terminal speed above the luminous flat disk under an approximation of the order of ( v / c ) ^ { 1 } .
We also examine the case where heating exists , and find that the flow properties are qualitatively similar to the case without heating .