My Experiences and Experiments with Transonic Flows Around Compact Objects

Abstract

In this work, we discuss the transonic properties of the accretion flow considering the black hole (hereafter BH) as the central object. During accretion, before crossing the horizon, flow passes through the saddle-type critical point located outside the event horizon. Depending on the input parameters of the flow, namely specific energy and angular momentum for adiabatic flow, advective accretion flow may possess multiple saddle type critical points and, in such cases, flow may experience discontinuous transition in the flow variables as an imprint of shock waves. Considering the generalized accretion flow that includes viscosity, magnetic field and radiative cooling mechanisms, we compute the global transonic accretion solutions containing shocks and examine the influence of flow parameters on the shock properties. We find that shocks form for widespread flow parameters and, subsequently, we calculate the critical values of both viscosity and accretion rate that cater shocks. We continue the search of shocked accretion solutions for two-temperature flow and obtain such solutions for the first time in the literature. Finally, we discuss the possible origin of mass loss from the accretion disk and show that launching of outflow continues to take place around rotating BHs having wide range of spin parameters (ak).