NGC 5548 spectra fit with the baseline plus an additional component. The X21 data and the best-fit blueshifted pion model with log(ξ) = 2 (Sect. 3.1) are shown in (a). Panels b and c: plot the X21 spectrum fit with the blueshifted single charge exchange of ionization temperature equal to 0.05 keV, and two charge exchange components of the same temperature. The C13 data with a single charge exchange component is shown in (d). The X21 spectrum with a redshifted charge exchange component (an ionization temperature equal to 0.1 keV) is displayed in (e). In all panels, the baseline model is plotted in red, and the baseline plus additional component is shown in blue. The relevant lines of the additional components (pion and cx) are also plotted below the data. The wavelengths of the transitions are given at the AGN restframe, and the intensities are scaled for clarity. For better comparison, the spectra and the models around the 18.4 Å feature are also shown in the insets.