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Department of Physics

Staff profile

Publication details for Prof Martin Ward

Roberts, T. P., Goad, M. R., Ward, M. J., Warwick, R. S., O'Brien, P. T., Lira, P. & Hands, A. D. P. (2001). The identification of an optical counterpart to the super-Eddington X-ray source NGC 5204 X-1. Monthly Notices of the Royal Astronomical Society 325(2): L7-L11.

Author(s) from Durham


We report the identification of a possible optical counterpart to the super-Eddington X-ray source NGC 5204 X-1. New Chandra data show that the X-ray source is point-like, with a luminosity of 5.2×10^39 erg/s (0.5-8 keV). It displays medium- and long-term X-ray variability in observations spanning a period of 20yr. The accurate Chandra position allows us to identify a blue optical continuum source (mv=19.7) at the position of NGC 5204 X-1, using newly obtained optical data from the INTEGRAL instrument on the William Herschel Telescope. The X-ray and optical source properties are consistent with the scenario in which we are observing the beamed X-ray emission of a high-mass X-ray binary in NGC 5204, composed of an O star with either a black hole or neutron star companion.


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