Supersonic and subsonic flows in general relativistic radiation hydrodynamics

TL;DR

This paper investigates stationary accretion flows in general relativistic radiation hydrodynamics, revealing the existence and characteristics of transonic, subsonic, and supersonic solutions under various conditions.

Contribution

It provides a detailed analysis of flow bifurcations, flow morphology, and the conditions for solution uniqueness in relativistic radiation hydrodynamics.

Findings

Transonic flows exist at low redshifts but disappear at high redshifts and luminosities.

Two flow branches (subsonic and supersonic) originate at a bifurcation point.

Boundary data influence solution uniqueness and maximal luminosity.

Abstract

We analyze stationary accretion of selfgravitating gas onto a compact center within general-relativistic radiation hydrodynamics. Spherical symmetry and thin gas approximation are assumed. Numerical investigation shows that transonic flows exist for small redshifts and they cease to exist for high redshifts and high luminosities. There exist two branches of flows (subsonic or supersonic) that originate at a bifurcation point and that embrace the set of subsonic solutions. The morphology of the set of subsonic solutions is essentially independent of redshifts and flows that belong to their boundary provide estimates of the gas abundance of subsonic solutions. It appears that prescribed boundary data guarantee uniqueness only of the bifurcation point, and that the latter has maximal luminosity.