Residuals for a joint fit with a spline model through the RGS1 (black), RGS2 (grey, excluding wavelength between 6.55 and 7.55 Å in the fit), Resolve and NuSTAR (not shown) instruments. For comparison we show the residuals to this model for Xtend (purple histogram) and MEG (orange); these last two instruments were not included in the fit. The red line is a fit to the RGS2 residuals, with model and parameters indicated in the inset.