Universality and backreaction in a general-relativistic accretion of steady fluids

TL;DR

This paper investigates how backreaction affects steady, spherically symmetric accretion of polytropic fluids onto black holes, revealing universal properties and a maximum mass accretion rate at a specific fluid-to-total mass ratio.

Contribution

It provides an analytic and numerical analysis of backreaction effects, showing the invariance of sonic point characteristics and a universal maximum accretion rate.

Findings

Backreaction preserves sonic point properties.

Maximum accretion rate occurs when fluid mass is one-third of total mass.

Universal behavior regardless of fluid abundance.

Abstract

The spherically symmetric steady accretion of polytropic perfect fluids onto a black hole is the simplest flow model that can demonstrate the effects of backreaction. The analytic and numerical investigation reveals that backreaction keeps intact most of the characteristics of the sonic point. For any such system, with the only free parameter being the relative abundance of the fluid, the mass accretion rate achieves maximal value when the mass of the fluid is universally 1/3 of the total mass.