The Ultra Luminous X-ray ( ULX ) source HLX-1 in the galaxy ESO 243-49 has an observed maximum unabsorbed X-ray luminosity of 1.3 \times 10 ^ { 42 } 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 M _ { \odot } .
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 .