Periodic mass loss from viscous accretion flows around black holes

Abstract

We investigate the behaviour of low angular momentum viscous accretion flows\naround black holes using Smooth Particle Hydrodynamics (SPH) method. Earlier,\nit has been observed that in a significant part of the energy and angular\nmomentum parameter space, rotating transonic accretion flow undergoes shock\ntransition before entering in to the black hole and a part of the post-shock\nmatter is ejected as bipolar outflows, which are supposed to be the precursor\nof relativistic jets. In this work, we simulate accretion flows having\ninjection parameters from the inviscid shock parameter space, and study the\nresponse of viscosity on them. With the increase of viscosity, shock becomes\ntime dependent and starts to oscillate when the viscosity parameter crosses its\ncritical value. As a result, the in falling matter inside the post-shock region\nexhibits quasi-periodic variations and causes periodic ejection of matter from\nthe inner disc as outflows. In addition, the same hot and dense post-shock\nmatter emits high energy radiation and the emanating photon flux also modulates\nquasi-periodically. Assuming a ten solar mass black hole, the corresponding\npower density spectrum peaks at the fundamental frequency of few Hz followed by\nmultiple harmonics. This feature is very common in several outbursting black\nhole candidates. We discuss the implications of such periodic variations.\n