Coronal ejection and heating in variable-luminosity X-ray sources

TL;DR

This paper explores how sudden changes in luminosity in X-ray sources can cause gas ejection or orbital tightening, potentially explaining coronal heating in accreting black holes and neutron stars.

Contribution

It introduces a theoretical framework linking luminosity fluctuations to gas dynamics and coronal heating in X-ray emitting astrophysical systems.

Findings

Luminosity increases above half the Eddington limit eject gas from star systems.

Decreases in luminosity tighten orbits of optically thin gas.

Luminosity fluctuations can significantly heat the X-ray corona.

Abstract

A sudden increase in stellar luminosity may lead to the ejection of a large part of any optically thin gas orbiting the star. Test particles in circular orbits will become unbound, and will escape to infinity (if radiation drag is neglected), when the luminosity changes from zero to at least one half the Eddington value, or more generally, from L to (L_Edd+L)/2 or more. Conversely, a decrease in luminosity will lead to the tightening of orbits of optically thin fluid. Even a modest fluctuation of luminosity of accreting neutron stars or black holes is expected to lead to substantial coronal heating. Luminosity fluctuations may thus account for the high temperatures of the X-ray corona in accreting black hole and neutron star systems.