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XMM­Newton CCF Release Note
XMM­CCF­REL­215
RGS individual CCD sensitivies and 2nd and 3rd order grating
e#ciencies
A.M.T. Pollock
June 29, 2006
1 CCF components
Name of CCF VALDATE List of Blocks changed XSCS flag
RGS1 QUANTUMEF 0015 1998­01­01T00:00:00 CCD DESC NO
RGA EFFCORR NO
RGS2 QUANTUMEF 0016 1998­01­01T00:00:00 CCD DESC NO
RGA EFFCORR NO
2 Changes
The sensitivity of individual CCDs has been checked by inspection of the nearly 1 million seconds
of raw data accumulated on Mkn421 throughout the mission as shown in Fig. 1. In the past,
the small di#erences between CCDs have been parameterised as equivalent thicknesses of SiO 2 .
In this release, they are coded more directly as individual CCD sensitivities in 5 new columns
CCD DESC(SENS M[1­5]), one for each order, with any non­zero thicknesses of SiO 2 reset to zero.
Adjustments were required for CCD2 only in both instruments. In RGS1 this amounts to 3.5% in
1st order and progressively less for higher orders. In RGS2 the 1st order correction is 11.4%.
Following the derivation of new 1st order spectra with the revised e#ective­area calibration de­
scribed in XMM­CCF­REL­216 that incorporates, among other things, these new individual CCD
sensitivities, it was also necessary to recalculate the 2nd and 3rd order corrections held in the
RGA EFFCORR extension. the results are shown in Fig. 2. The agreement between the three
independent sets of data is good. There are di#erences of the order of 10% in comparison with the
previous values.
1

XMM­Newton CCF Release XMM­CCF­REL­215 Page: 2
Figure 1: Data accumulated throughout the mission on Mkn421 plotted in detector coordinates.
RGS1 on the right and RGS2 on the left. Sensitivity corrections were required for CCD2 in both
RGS instruments.
Figure 2: New 2nd and 3rd order corrections for the RGS instruments using the accumulated data of
Mkn421 throughout the mission. RGS1 data are shown in red before the loss of the CCD7 electronics
in rev 0135 and in green after. RGS2 from the whole mission are in blue. The early RGS1 data
were supplemented by two observations of PKS2155­304 from rev 0087. The upper branch is the
2nd order, the lower 3rd order. The solid lines show the tabulation in the new CCF release.

XMM­Newton CCF Release XMM­CCF­REL­215 Page: 3
3 Scientific Impact of this Update
Unknown.
4 Estimated Scientific Quality
Improved consistency between the long wavelengths sampled by CCD2 in RGS1 and RGS2 and
the rest of the spectrum. Because the 2nd and 3rd order corrections are empirical, the improved
consistency ensured by this calibration update will allow observers to be more confident in their use
of especially 2nd order spectra in analysis. The use of the SAS task rgsfluxer is recommended in
this respect and should be encouraged in order to compensate in part with second order for the loss
of data from RGS2 CCD7.
5 Test procedures & results
This CCF is part of the overall calibration e#ort whose final results are described in the new RGS
e#ective area model described in XMM­SOC­CAL­SRN­0216.
6 Expected Updates
None expected.