An Intermediate-mass Black Hole of Over 500 Solar Masses in the Galaxy ESO 243-49

TL;DR

This paper reports the discovery of a variable X-ray source in galaxy ESO 243-49, providing strong evidence for an intermediate-mass black hole of at least 500 solar masses, bridging the gap between stellar and supermassive black holes.

Contribution

It presents the strongest observational evidence to date for an intermediate-mass black hole, supporting its existence and significance in black hole evolution.

Findings

Detected a luminous, variable X-ray source in ESO 243-49

Estimated black hole mass of at least 500 solar masses

Provides evidence linking stellar and supermassive black holes

Abstract

Ultra-luminous X-ray sources are extragalactic objects located outside the nucleus of the host galaxy with bolometric luminosities >10^39 erg s^-1. These extreme luminosities - if the emission is isotropic and below the theoretical (i.e. Eddington) limit, where the radiation pressure is balanced by the gravitational pressure - imply the presence of an accreting black hole with a mass of ~10^2-10^5 times that of the Sun. The existence of such intermediate mass black holes is in dispute, and though many candidates have been proposed, none are widely accepted as definitive. Here we report the detection of a variable X-ray source with a maximum 0.2-10 keV luminosity of up to 1.2 x 10^42 erg s^-1 in the edge-on spiral galaxy ESO 243-49, with an implied conservative lower limit of the mass of the black hole of ~500 Msun. This finding presents the strongest observational evidence to date for the existence of intermediate mass black holes, providing the long sought after missing link between the stellar mass and super-massive black hole populations.