Detalles de publicación
PP 014116
Optical study of the hyper-luminous X-ray source 2XMM J011942.7+032421
1. Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, SPAIN
2. Dep. de Astrof\'\i sica, Universidad de la Laguna, E-38206 Tenerife, SPAIN
3. Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4, Canada
We present the identification and characterization of the optical counterpart
to 2XMM J011942.7+032421, one of the most luminous and distant ultra-luminous
X-ray sources (ULXs). The counterpart is located near a star forming region
in a spiral arm of the galaxy NGC~470 with u, g, and r magnitudes of
21.53, 21.69, and 21.71 mags, respectively. The luminosity of the counterpart
is much larger than that of a single O-type star, indicating that it may be a stellar cluster. Our optical spectroscopic observations confirm the association of the X-ray source and the optical counterpart with its host galaxy NGC~470,
which validates the high, ~> 10^41 erg/s, X-ray luminosity of the source.
Its optical spectrum is embedded with numerous emission lines, including
H recombination lines, metallic forbidden lines and more notably the high-ionization HeII (lambda 4686 A) line. This line shows a large velocity dispersion of $\simeq$ 410 km/s, consistent with the existence of a compact (< 5 AU) highly-ionized accretion disc rotating around the central X-ray source.
The ~1.4 x 10^37 erg/s luminosity of the HeII line emission makes the source one of the most luminous ULXs in the emission of that line. This, together with the high X-ray luminosity and the large velocity dispersion of the HeII emission, suggests that the source is an ideal candidate for more extensive follow-up observations for understanding the nature of hyper-luminous X-ray sources, a more luminous subgroup of ULXs and more likely candidates for intermediate-mass black holes.
to 2XMM J011942.7+032421, one of the most luminous and distant ultra-luminous
X-ray sources (ULXs). The counterpart is located near a star forming region
in a spiral arm of the galaxy NGC~470 with u, g, and r magnitudes of
21.53, 21.69, and 21.71 mags, respectively. The luminosity of the counterpart
is much larger than that of a single O-type star, indicating that it may be a stellar cluster. Our optical spectroscopic observations confirm the association of the X-ray source and the optical counterpart with its host galaxy NGC~470,
which validates the high, ~> 10^41 erg/s, X-ray luminosity of the source.
Its optical spectrum is embedded with numerous emission lines, including
H recombination lines, metallic forbidden lines and more notably the high-ionization HeII (lambda 4686 A) line. This line shows a large velocity dispersion of $\simeq$ 410 km/s, consistent with the existence of a compact (< 5 AU) highly-ionized accretion disc rotating around the central X-ray source.
The ~1.4 x 10^37 erg/s luminosity of the HeII line emission makes the source one of the most luminous ULXs in the emission of that line. This, together with the high X-ray luminosity and the large velocity dispersion of the HeII emission, suggests that the source is an ideal candidate for more extensive follow-up observations for understanding the nature of hyper-luminous X-ray sources, a more luminous subgroup of ULXs and more likely candidates for intermediate-mass black holes.