Stacked residual spectra in the [12′−15′] annulus for two sets of blank-sky observations sorted by their values of inFOV − outFOV. The left-hand panel shows the low-contamination dataset (inFOV − outFOV < 0.03 cts/s) whereas in the right-hand panel we are selecting only highly contaminated observations (0.08 < inFOV − outFOV < 0.18 cts/s). The residuals were fit beyond 2 keV with a power law indicated by the solid lines. The bottom panels show the residuals compared to the model.