Formation of non-steady outflows and QPOs around black hole

TL;DR

This paper investigates how viscous accretion flows around black holes produce unsteady outflows and QPOs, linking shock oscillations and jet formation to observable high-energy radiation modulations.

Contribution

It introduces a model showing shock oscillations driven by viscosity changes lead to periodic outflows and QPOs in black hole accretion disks.

Findings

Shock transitions trigger bipolar outflows.

Increased viscosity causes shock oscillations.

QPOs are linked to shock oscillation frequencies.

Abstract

We study the time dependent properties of sub-Keplerian viscous accretion flow around the black holes. We find that rotating matter feels centrifugal barrier on the way towards the black holes and eventually, shock transition is triggered allowing a part of the post-shock matter to eject out as bipolar outflow. This outflowing matters are supposed to be the precursor of relativistic jets. As viscosity is increased, shock becomes unsteady and start to oscillate when viscosity reached its critical value. This causes the inner part of the disk unsteady resulting periodic ejection of matter from the post-shock region. Also, the same hot and dense post-shock matter emits high energy radiation which modulates quasi-periodically. The power density spectra confirms this features as most of the power is concentrated at a narrow frequency range --- a characteristics (i. e. Quasi-Periodic Oscillation) commonly seen in several outbursting black hole candidates.