Residuals, plotted in terms of sigma with error bars of size one, for the XRT spectrum, modelled with an absorbed power-law component (Γ ~ 1.5, N_H ~ 1.8 × 10²²cm^-2). A deep absorption trough is seen in the iron K band, possibly associated with a broad absorption feature (dashed red line). The dotted red line marks the position where the neutral Fe Kα emission line is expected (and marginally detected).