Viscosity parameter in dissipative accretion flows with mass outflow around black holes

Abstract

Numerical hydrodynamic simulation of inviscid and viscous flows have shown that significant outflows could be produced from the CENtrifugal pressure supported BOundary Layer or CENBOL of an advective disk. However, this barrier is weakened in presence of viscosity, more so, if there are explicit energy dissipations at the boundary layer itself. We study effects of viscosity and energy dissipation theoretically on the outflow rate and show that as the viscosity or energy dissipation (or both) rises, the prospect of formation of outflows is greatly reduced, thereby verifying results obtained through observations and numerical simulations. Indeed, we find that in a dissipative viscous flow, shocks in presence of outflows can be produced only if the Shakura-Sunyaev viscosity parameter α is less than 0.2. This is a direct consequence of modification of the Rankine-Hugoniot relation across the shock in a viscous flow, when the energy dissipation and mass loss in the form of outflows from the post-shock region are included. If we ignore the effects of mass loss altogether, the standing dissipative shocks in viscous flows may occur only if α < 0.27. These limits are tighter than the absolute limit of α = 0.3 valid for a situation when the shock itself neither dissipates energy nor any outflow is formed. We compute typical viscosity parameters required to understand spectral and temporal properties of several black hole candidates such as GX399-4, MAXI J1659-152 and MAXI J1836-194 and find that required α are indeed well within our prescribed limit.

9 pages, 7 figures

References in corpus (9)

• Accretion disc viscosity: how big is alpha?
• Angular Momentum Transport in Accretion Disks: Scaling Laws in MRI-driven Turbulence
• Evolution of the quasi-periodic oscillation frequency in GRO J1655-40 -- Implications for accretion disk dynamics
• Oscillating shocks in the low angular momentum flows as a source of variability of accreting black holes
• Effects of Compton Cooling on Outflow in a Two Component Accretion Flow around a Black Hole: Results of a Coupled Monte Carlo-TVD Simulation
• Is Compton cooling sufficient to explain evolution of observed quasi-periodic oscillations in Outburst sources?
• Quasi-Spherical, Time-Dependent Viscous Accretion Flow: One-Dimensional Results
• Spectral signatures of dissipative standing shocks and mass outflow in presence of Comptonization around a black hole
• Propagating Oscillatory Shock Model for QPOS in GRO J1655-40 During the March 2005 Outburst

Cited by in corpus (2)

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