Mg-region spectra of high-hardness (left panel, black) and low-hardness (right panels, blue) periods. Residuals to best fit model are shown in black/blue, residuals to a power law without the line components in orange. The upper right panel shows a fit with five independent absorption lines. The lower right panel shows a fit using a template for Mg-series from Mg xi to iv (reference energies according to Behar & Netzer 2002, indicated by solid lines) with one Doppler shift for all lines. Spectra normalized to their respective power-law continua are shown in Fig. 8. For the high-hardness region, lines identified are indicated and labeled. For the low-hardness region, we refer to the Tables 5 and 6 for the identified lines.