A REDSHIFT FOR THE INTERMEDIATE-MASS BLACK HOLE CANDIDATE HLX-1: CONFIRMATION OF ITS ASSOCIATION WITH THE GALAXY ESO 243-49
- Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom)
- Universite de Toulouse, UPS, CESR, 9 Avenue du Colonel Roche, F-31028 Toulouse Cedex 9 (France)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-67, Cambridge, MA 02138 (United States)
- School of Physics and Astronomy, University of Southampton, Hampshire SO17 1BJ (United Kingdom)
In this Letter, we report a spectroscopic confirmation of the association of HLX-1, the brightest ultra-luminous X-ray (ULX) source, with the galaxy ESO 243-49. At the host galaxy distance of 95 Mpc, the maximum observed 0.2-10 keV luminosity is 1.2 x 10{sup 42} erg s{sup -1}. This luminosity is {approx}400 times above the Eddington limit for a 20 M {sub sun} black hole and has been interpreted as implying an accreting intermediate-mass black hole with a mass in excess of 500 M {sub sun} (assuming that the luminosity is a factor of 10 above the Eddington value). However, a number of other ULX sources have been later identified as background active galaxies or foreground sources. It has recently been claimed that HLX-1 could be a quiescent neutron star X-ray binary at a Galactic distance of only 2.5 kpc, so a definitive association with the host galaxy is crucial in order to confirm the nature of the object. Here, we report the detection of the H{alpha} emission line for the recently identified optical counterpart at a redshift consistent with that of ESO 243-49. This finding definitively places HLX-1 inside ESO 243-49, confirming the extreme maximum luminosity and strengthening the case for it containing an accreting intermediate-mass black hole of more than 500 M {sub sun}.
- OSTI ID:
- 21452791
- Journal Information:
- Astrophysical Journal Letters, Vol. 721, Issue 2; Other Information: DOI: 10.1088/2041-8205/721/2/L102; ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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