Confidence contours corresponding to ΔC = 2.30 (solid), 4.61 (dashed), 9.21 (dotted) in the Γ vs. flux plane, as obtained from a separate analysis of pn (blue curves, with best-fit value marked by a dot) and MOS (red curves, cross) spectra. Two examples are shown to be representative of the brightest (J0304−00, ∼1100 cumulative net counts) and faintest (J1201+01, ∼200 counts) sources in our sample. The agreement between pn and MOS is always remarkable, and well within the measurement uncertainties even for spectra of relatively low quality.