SAS Watchout

Why has the flux I get from fitting XMM-Newton EPIC spectra changed in SAS v22?

In SAS v22.0 the parameter defaults in arfgen whave changed so that two emprical corrections are applied to the effective areas.

applyxcaladjustment = yes

this modifies the effective area of the MOS cameras so that they return fluxes which are as close as possible to the flux returned by the EPIC-pn camera (see CAL-SRN-0382 and CAL-SRN-0410 for details).

applyabsfluxcorr = yes

an absolute flux correction, applicable to all EPIC cameras, which modifies effective areas in the 3-12 keV band so that EPIC spectra match more closely spectral slopes returned by fits to NuSTAR data (see CAL-SRN-388).