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XMM­Newton CCF Release Note
XMM­CCF­REL­212
Tuning RGS Instrumental MgF 2 Absorption with Mkn421
A.M.T. Pollock
June 27, 2006
1 CCF components
Name of CCF VALDATE List of Blocks
changed
XSCS flag
RGS1 EXAFS 0005 1999­01­01T00:00:00 MgF2­P­CCD1 NO
MgF2­P­CCD2
MgF2­P­CCD3
MgF2­P­CCD4
MgF2­P­CCD5
MgF2­P­CCD6
MgF2­P­CCD7
MgF2­P­CCD8
MgF2­P­CCD9
RGS2 EXAFS 0005 1999­01­01T00:00:00 MgF2­P­CCD1 NO
MgF2­P­CCD2
MgF2­P­CCD3
MgF2­P­CCD4
MgF2­P­CCD5
MgF2­P­CCD6
MgF2­P­CCD7
MgF2­P­CCD8
MgF2­P­CCD9
2 Changes
This release improves the description of the weak instrumental absorbtion feature near 17.9 š A due to
MgF 2 in the RGS CCDs by exploiting the high statistics of the roughly 1 million seconds accumulated
on the bright smooth continuum of blazar Mkn421 throughout the mission between revs 0084 and
1084. The previous release was described in XMM­SOC­CAL­SRN­0171
1

XMM­Newton CCF Release XMM­CCF­REL­212 Page: 2
mkn421/add_newexaf_rgs1-mkn421/add_oldexaf_rgs1
17.5 18.0 18.5 19.0
Wavelength (å)
0.0120
0.0125
0.0130
0.0135
0.0140
0.0145
0.0150
Photons/cm 2
/s
mkn421/add_newexaf_rgs1-mkn421/add_oldexaf_rgs1
17.5 18.0 18.5 19.0
Wavelength (å)
-0.0006
-0.0004
-0.0002
0.0000
0.0002
0.0004
0.0006
0.0008
Photons/cm 2
/s
(CdV) Wed Apr 12 12:05:37 2006
mkn421/add_newexaf_rgs2-mkn421/add_oldexaf_rgs2
17.0 17.5 18.0 18.5
Wavelength (å)
0.0125
0.0130
0.0135
0.0140
0.0145
Photons/cm 2
/s
mkn421/add_newexaf_rgs2-mkn421/add_oldexaf_rgs2
17.0 17.5 18.0 18.5
Wavelength (å)
-0.0010
-0.0005
0.0000
0.0005
0.0010
Photons/cm
2
/s
(CdV) Wed Apr 12 12:07:01 2006
Figure 1: Details of first­order spectra of RGS1 (right) and RGS2 (left) of Mkn421 accumulated
throughout the mission in order to maximise statistics. The upper panels show the spectra calculated
with the new release in red and the previous release in green, while the lower panels show the
di#erence.
3 Scientific Impact of this Update
Reduced risk of confusing an instrumental feature with absorption in the intergalactic medium, for
example.
4 Estimated Scientific Quality
Systematic flux uncertainties near the Flourine edge reduced to about 2%.
5 Test procedures & results
The equivalent width of the instrumental Fluorine feature is quite low and thus not easy to see in
single observations of even strong sources. Fig. 1 shows RGS 1st­order accumulated mean spectra
of Mkn421 calculated with the old and new EXAFS CCFs. The instrumental absorbtion feature
near 17.9 š A due to MgF 2 has been reduced in the new release to a level consistent with the general
noise level.
6 Expected Updates
With the routine accumulation of calibration data on Mkn421, it should be possible to review. the
instrumental absorption data every few years.