A re-analysis of the iron line in the XMM-Newton data from the low/hard state in GX339-4

The detection of an extremely broad iron line in XMM-Newton MOS data from the low/hard state of the black hole binary GX339-4 is the only piece of evidence which unambiguously conflicts with the otherwise extremely successful truncated disc interpretation of this state. However, it also conflicts with some aspect of observational data for all other alternative geometries of the low/hard state, including jet models, making it very difficult to understand. We re-analyse these data and show that they are strongly affected by pile-up even with extensive centroid removal as the source is ~200 times brighter than the recommended maximum count rate. Instead, we extract the simultaneous PN timing-mode data which should not be affected by pile-up. These show a line which is significantly narrower than in the MOS data. Thus these data are easily consistent with a truncated disc, and indeed, strongly support such an interpretation.