# Effects of adiabatic index on the sonic surface and time variability of low angular momentum accretion flows

## TL;DR

This study investigates how the adiabatic index influences the critical points, shock dynamics, and variability in low angular momentum accretion flows onto black holes using relativistic hydrodynamic simulations.

## Contribution

It provides the first detailed analysis of the impact of adiabatic index on shock behavior and variability in relativistic accretion flows near black holes.

## Key findings

- Adiabatic index significantly affects shock position and oscillation frequency.
- Variations in adiabatic index alter mass accretion rates.
- Results have implications for understanding microquasar variability.

## Abstract

We study the role of adiabatic index in determining the critical points in the transonic low angular momentum accretion flow onto a black hole. We present the general relativistic 2D hydrodynamic simulations of axisymmetric, inviscid accretion flows in a fixed Kerr black hole gravitational field. A relativistic fluid where its bulk velocity is comparable to the speed of light, flowing in the accretion disk very close to the horizon can be described by an adiabatic index of 4/3 < {\gamma} < 5/3. The time dependent evolution of the shock position and respective effects on mass accretion rate and oscillation frequency with varying adiabatic index is discussed in the context of the observed microquasars.