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Durham University

Department of Physics

Staff profile

Publication details for Prof Tim Roberts

Walton, D.J., Gladstone, J.C., Roberts, T.P. & Fabian A.C. (2011). A large catalogue of ultraluminous X-ray source candidates in nearby galaxies. Astronomische Nachrichten 332(4): 354-357.

Author(s) from Durham


Since their discovery, Ultraluminous X-ray sources (ULXs) have attracted attention due to their combination of extreme luminosities and extra-nuclear locations. However, they are a fairly rare phenomenon, and attempts to investigate the general properties of the population have been hindered by a relative lack of known sources. Here, we present a large catalogue of ULX candidates including 655 detections of 475 discrete sources, based on the 2XMM Serendipitous Survey. To demonstrate the potential of such a resource, we present some scientific analysis of this population, focusing on the spectral turnover seen, often at ∼6 keV, in the highest quality ULX data. We also demonstrate how the recent reflection and Comptonisation interpretations of this feature may be distinguished observationally in the future, specifically using NGC 4517 ULX1, a previously unanalysed source with high quality data, as an example case.