Unfolded spectrum and residuals adopting Model 1 (left panels) and Model 2 (right panels). The black, red, green, and blue data correspond to the first-order MEG of spectra A, B, C, and D, respectively. The cyan, purple, yellow, and orange data correspond to first-order HEG spectrum of spectra A, B, C, and D, respectively. The prominent absorption lines in residuals of Model 1 (bottom left panel) are associated with the presence of Ne X, Mg XII, Si XIV, S XVI, and Fe XXVI ions.