Best fits of CAL 83 (left) and RX J0513.9–6951 (right) spectra (top). The observed spectra (Chandra, black curves) and the model fits (red curves) are shown. Residuals and the smoothed residuals (magenta curves) of the fits (bottom). Any possible identifications of the most prominent residual features as resonance lines of highly charged ions of some heavy elements are indicated. The best-fit parameters are presented in Table 2.