RGS spectrum in the 7 − 27 Å range, obtained by stacking all XMM-Newton observations. The red curve shows the model with three cie components (blueshifted, redshifted, and rest-frame), on top of the continuum. The rest-frame wavelengths of the most relevant lines are labelled. The dotted (dashed) lines show the velocity shift for the blueshifted (redshifted) lines. The data are grouped by a factor of 10.