Abstract:
We investigate the behaviour of low angular momentum viscous accretion flows around black
holes using smooth particle hydrodynamics method. Earlier, it has been observed that in a
significant part of the energy and angular momentum parameter space, rotating transonic
accretion flow undergoes shock transition before entering in to the black hole and a part of
the post-shock matter is ejected as bipolar outflows, which are supposed to be the precursor
of relativistic jets. In this work, we simulate accretion flows having injection parameters from
the inviscid shock parameter space, and study the response of viscosity on them. With the
increase of viscosity, shock becomes time dependent and starts to oscillate when the viscosity
parameter crosses its critical value. As a result, the in falling matter inside the post-shock region
exhibits quasi-periodic variations and causes periodic ejection of matter from the inner disc as
outflows. In addition, the same hot and dense post-shock matter emits high energy radiation
and the emanating photon flux also modulates quasi-periodically. Assuming a 10 Mꙩ black
hole, the corresponding power density spectrum peaks at the fundamental frequency of few
Hz followed by multiple harmonics. This feature is very common in several outbursting black
hole candidates. We discuss the implications of such periodic variations.
