Panel a: XMM-Newton spectra with respect to a power-law only modelling in the 4–10 keV band. Panel b: low and high energy residuals still present after the WA was included in the modelling. Panel c: final data-to-model ratio after the inclusion of Gaussian components. A few unmodelled features still populate the energy range between 1.5 and 2.5 keV. However some of these may be directly attributed to the detector systematics.