The accretion disc, jets and environment of the intermediate mass black hole candidate ESO 243-49 HLX-1

TL;DR

This paper models X-ray data of HLX-1, supporting its classification as an intermediate mass black hole powered by accretion, and presents evidence of jet ejection and environmental analysis.

Contribution

It provides a comprehensive modeling of HLX-1's X-ray variability and supports the intermediate mass black hole hypothesis with new evidence of jet activity and environmental context.

Findings

X-ray luminosity varies by a factor of 40

Spectral state transitions resemble black hole binaries

Evidence of transient radio jet ejection

Abstract

The Ultra Luminous X-ray (ULX) source HLX-1 in the galaxy ESO 243-49 has an observed maximum unabsorbed X-ray luminosity of 1.3e42 erg/s (0.2-10.0 keV). From the conservative assumption that this value exceeds the Eddington limit by at most a factor of 10, the minimum mass is then 500 solar masses. The X-ray luminosity varies by a factor of 40 with an apparent recurrence timescale of approximately one year. This X-ray variability is associated with spectral state transitions similar to those seen in black hole X-ray binaries. Here we discuss our recent modelling of all the X-ray data for HLX-1 and show that it supports the idea that this ULX is powered by sub- and near Eddington accretion onto an intermediate mass black hole. We also present evidence for transient radio emission which is consistent with a discrete jet ejection event as well as comment on the nature of the environment around HLX-1 in light of recent Hubble Space Telescope photometry.