ISOTHERMAL SHOCKS IN ADIABATIC BLACK-HOLE ACCRETION FLOWS

This paper presents global solutions of adiabatic accretion flows with isothermal shocks in the potential of a non-rotating black hole. It i s known that in the previously studied cases, where flow including sho ck is either entirely adiabatic or entirely isothermal, there can be n o more than one stable shock solution, and the solution can only be of the alpha-x type; however, the solution topology in the present case shows new remarkable characteristics: for the same flow parameters the re can be two stable shock solutions satisfying the physical boundary conditions, and the solution can be of three types, namely alpha-x, x- alpha, and alpha-alpha type. In addition, shocks in the present case o ccur for a parameter region that is different from that for Rankine-Hu goniot shocks to occur. These results greatly increase the possibiliti es of shock formation in astrophysical hows. It is also noted that in the present case the efficiency of energy release at the shock can be as high as a few percent. Finally, a brief comparison is made between shocked inviscid hows and two types of shock-free viscous flow, namely that of Shakura and Sunyaev (1973, AAA 09.066.049) and that of Naraya n and Yi (1994, AAA 61.064.083).