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epiclccorr (epiclccorr-1.23.1) [xmmsas_20230412_1735-21.0.0]

Absolute Corrections

The first version of epiclccorr will be optimised to correct time series extracted from point sources. The Absolute Correction will be finally applied to the corrected source TS background substracted.

A coarse spectrum (50 eV bins) will be produced by evselect from the source region, over the energy range used in the constructions of the TS. This will be used with arfgen to find the effective area array for the source as a function of photon energy.

arfgen will be executed twice; The fist call with the spectrum in the real position (off-axis) and with the standard default parameters.

A second call to arfgen using the parameters (withsourcepos=yes sourcecoords="tel" sourcex=0 sourcey=0 filterdss=no withdetbounds=yes withbadpixcorr=N modelee=N detmaptype=flat detxbins=1 detybins=1) will calculate the ideal effective area of this camera/filter combination with no losses.

By dividing the effective area, returned by arfgen for an infinite on-axis extraction region by the effective area returned from the actual extraction region, we will obtain an array of absolute corrected factors (Fig.see figure:). These will be weighted by the source spectrum to find a single absolute correction factor.

\epsfig{file=area_ratio.epsi,width=.9\textwidth}
we show the ratio of an off-axis (aprox. 10 arcmin) vs. on-axis ARF values with respect to the energy. The ratio remains almost constant up to 4 keV.

XMM-Newton SOC -- 2023-04-16