XMM-Newton EPIC observations of the ultraluminous X-ray source NGC 5204 X-1

Abstract

We present the results of two XMM-Newton observations of the ultraluminous X-ray source NGC 5204 X-1. The EPIC spectra are well fitted by the standard spectral model of a black hole X-ray binary, comprising a soft multicolour disc blackbody component plus a harder power-law continuum. The cool (kT_in~ 0.2 keV) inner-disc temperature required by this model favours the presence of an intermediate-mass black hole in this system, though we highlight a possible anomaly in the slope of the power-law continuum in such fits. We discuss the interpretation of this and other, non-standard spectral modelling of the data.