Distribution in energy (observed frame) of the features detected via blind search. The energy bins are 0.2 keV wide. Top panels: results of the unobscured dataset (U1, U2a, U2b, U3), while the bottom panels refer to the obscured datasets (O1, O2). Left panels: detections of emission lines are reported (red), while the right panels report detections of absorption lines (blue): in both cases, the darker the colour the higher the significance, i.e. the measured Δχ². The percentage on the y axes is the ratio between the number of detections in each bin and the total number of spectra for the two sets of observations (56 in total for the unobscured, and 32 in total for the obscured). The dotted line reported in all four figures is the nominal energy of the Fe Kα and is shown purely as a visual reference. The letters A–E indicate the clusters of lines that globally reach a significance ≳3σ, as indicated in Table 2 and described in Sect. 3.4.