Test of the 4-blackbody combinations with xspec. The open diamonds show the diskbb model while the filled diamonds show the XMM-Newton unfolded spectrum. The set of best blackbody combinations with column density <10²² cm^-2 are shown in panel a). A subset with column densities between 1−2.5 × 10²¹ cm^-2 is shown in panel b). Only in the combinations left in panel c) are the associated photoionization models fulfilling the observed upper limit on the [Ne v] flux. For simplicity, we plot the X-ray spectra of panel c) with the same luminosity as for the other panels, but in reality an increased luminosity is used, according to Sect. 5.3. In each panel, the colors indicate the relative variation of the χ² among the plotted combinations (lower χ² in red, larger χ² in blue).