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XMM­Newton CCF Release Note
XMM­CCF­REL­235
EPIC MOS Quantum E#ciency
S.F.Sembay
6 August 2007
1 CCF components
Name of CCF VALDATE Blocks changed XSCS flag
EMOS1 QUANTUMEF 0017.CCF 2000­01­01 QE TOTAL NO
EMOS2 QUANTUMEF 0017.CCF 2000­01­01 QE TOTAL NO
2 Changes
The EPIC­MOS Quantum e#ciency has been adjusted by applying a multiplicative cor­
rection factor. This reduces the low energy QE by a maximum of 20% at the O edge.
3 Scientific Impact of this Update
The change to the overall quantum e#ciency (QE) of the central CCDs of both MOS
detectors has been made by increasing the depths of edges at the C, N and O energies.
Ground calibration measurements below 1 keV had obvious systematic discrepancies with
any plausible model of the CCD QE so the model initially adopted was informed mostly
by physical measurements of the surface structure of the CCD. Cross­calibration with the
most recent calibration of the EPIC­pn and RGS has provided strong evidence that this
model required adjustment. Nitrogen and Oxygen are constituents of the surface layers
of the CCDs and the level of increase of these depths is within the accuracy of physical
measurements of the CCD structure. Carbon is not a natural layer on the CCD. It has
been added to the QE model primarily because an additional edge at this energy is most
compatible with the exisiting redistribution function. There is no evidence for a signicant
change in these additional layers since launch and the new QE model is in fact marginally
in better agreement with the ground calibration measurements.
1

Figure 1: The form of the mathematical correction applied to the Quantum E#ciency
4 Estimated Scientific Quality
The multiplicative correction factor to the Quantum E#ciency is shown in Fig.1. The
same factor was applied to both MOS1 and MOS2 as this correction was equally applicable
to both detectors within the errors of the calibration data.
5 Expected Updates
Nothing forseen for these particular changes.
6 Test procedures and results
The MOS data from observations of the SNR 1E0102 were compared with a detailed
spectral model recently derived from high resolution RGS data. The result of folding
the model through the MOS response, with no renormalistion, is shown in the next two
figures. The adjusted QE (CCF 0017) clearly gives a better fit to the model around the
2

0.1
1
10
normalized
counts/sec/keV
Black (qe16) Red (qe17)
1ES0102 REV 0065 MOS1
1
0.2 0.5
-100
-50
0
sign(d-m)*C
channel energy (keV)
Figure 2: The MOS1 spectrum of the SNR 1E0102 compared with a model derived from RGS data folded
through the MOS response. The black line is with QE CCF 0016 and the red line is with QE CCF 0017.
The model has not been renormalised.
Oxygen lines than the QE in CCF 0016. Discrepancies in the fit at lowest and highest
energies in the energy band shown may due to uncertainties in the model parameters and
the RGS calibration at the extreme ends of the detector passband.
The e#ect of the QE adjustment was also compared to the cross­calibration with the
EPIC­pn. MOS1, MOS2 and pn data from 117 broad band AGN were spectrally fit and
fluxes derived in selected energy bands. Figs. 4 and 5 show the distribution of these
fluxes. The e#ect of the QE change is to increase the MOS fluxes below 1 KeV leaving
a generally energy­independent o#set in the derived fluxes between the MOS cameras
and the pn of around 5--10%. This makes the broad band spectral slope more consistent
between the cameras. With the previous calibration, MOS produced lower fluxes than pn
at low energies and higher fluxes at higher energies.
7 Comments
None
3

0.1
1
10
normalized
counts/sec/keV
Black (qe16) Red (qe17)
1ES0102 REV 0065 MOS2
1
0.2 0.5
-100
-50
0
sign(d-m)*C
channel energy (keV)
Figure 3: As previous figure, but for MOS2
4

0
10
20
30
40
0.5­2.0
0.6 0.8 1.0 1.2 1.4
statistical basis: 117 observations
relative flux in different bands [Joined fit = 1]
pn
MOS1
MOS2
RGS1
RGS2
xmmsas_20060628_1801­7.0.0_ccf_pub
0
10
20
30
2.0­10.0
0.6 0.8 1.0 1.2 1.4
statistical basis: 117 observations
relative flux in different bands [Joined fit = 1]
pn
MOS1
MOS2
RGS1
RGS2
xmmsas_20060628_1801­7.0.0_ccf_pub
0
5
10
15
0.15­0.33
0.6 0.8 1.0 1.2 1.4
statistical basis: 117 observations
relative flux in different bands [Joined fit = 1]
pn
MOS1
MOS2
RGS1
RGS2
xmmsas_20060628_1801­7.0.0_ccf_pub
0 5
10
15
20
25
30
0.33­0.54
0.6 0.8 1.0 1.2 1.4
statistical basis: 117 observations
relative flux in different bands [Joined fit = 1]
pn
MOS1
MOS2
RGS1
RGS2
xmmsas_20060628_1801­7.0.0_ccf_pub
0 5
10
15
20
25
30 35
0.54­0.85
0.6 0.8 1.0 1.2 1.4
statistical basis: 117 observations
relative flux in different bands [Joined fit = 1]
pn
MOS1
MOS2
RGS1
RGS2
xmmsas_20060628_1801­7.0.0_ccf_pub
0
10
20
30
0.85­1.5
0.6 0.8 1.0 1.2 1.4
statistical basis: 117 observations
relative flux in different bands [Joined fit = 1]
pn
MOS1
MOS2
RGS1
RGS2
xmmsas_20060628_1801­7.0.0_ccf_pub
0
10
20
30
1.5­4.0
0.6 0.8 1.0 1.2 1.4
statistical basis: 117 observations
relative flux in different bands [Joined fit = 1]
pn
MOS1
MOS2
RGS1
RGS2
xmmsas_20060628_1801­7.0.0_ccf_pub
0
10
20
30
4.0­10.0
0.6 0.8 1.0 1.2 1.4
statistical basis: 117 observations
relative flux in different bands [Joined fit = 1]
pn
MOS1
MOS2
RGS1
RGS2
xmmsas_20060628_1801­7.0.0_ccf_pub
Figure 4: The relative normalisations of the XMM instruments after joint fits to 117 bright AGN, using
the MOS QE CCF 0016.
5

0
10
20
30
40
50
0.5­2.0
0.6 0.8 1.0 1.2 1.4
statistical basis: 118 observations
relative flux in different bands [Joined fit = 1]
pn
MOS1
MOS2
RGS1
RGS2
xmmsas_20070708_1801­7.1.0_CCF_prepub
0
10
20
30
2.0­10.0
0.6 0.8 1.0 1.2 1.4
statistical basis: 118 observations
relative flux in different bands [Joined fit = 1]
pn
MOS1
MOS2
RGS1
RGS2
xmmsas_20070708_1801­7.1.0_CCF_prepub
0
5
10
15
20
0.15­0.33
0.6 0.8 1.0 1.2 1.4
statistical basis: 118 observations
relative flux in different bands [Joined fit = 1]
pn
MOS1
MOS2
RGS1
RGS2
xmmsas_20070708_1801­7.1.0_CCF_prepub
0 5
10
15
20
25
30
0.33­0.54
0.6 0.8 1.0 1.2 1.4
statistical basis: 118 observations
relative flux in different bands [Joined fit = 1]
pn
MOS1
MOS2
RGS1
RGS2
xmmsas_20070708_1801­7.1.0_CCF_prepub
0
10
20
30
40
0.54­0.85
0.6 0.8 1.0 1.2 1.4
statistical basis: 118 observations
relative flux in different bands [Joined fit = 1]
pn
MOS1
MOS2
RGS1
RGS2
xmmsas_20070708_1801­7.1.0_CCF_prepub
0
10
20
30
40
50
0.85­1.5
0.6 0.8 1.0 1.2 1.4
statistical basis: 118 observations
relative flux in different bands [Joined fit = 1]
pn
MOS1
MOS2
RGS1
RGS2
xmmsas_20070708_1801­7.1.0_CCF_prepub
0
10
20
30
1.5­4.0
0.6 0.8 1.0 1.2 1.4
statistical basis: 118 observations
relative flux in different bands [Joined fit = 1]
pn
MOS1
MOS2
RGS1
RGS2
xmmsas_20070708_1801­7.1.0_CCF_prepub
0
10
20
30
4.0­10.0
0.6 0.8 1.0 1.2 1.4
statistical basis: 118 observations
relative flux in different bands [Joined fit = 1]
pn
MOS1
MOS2
RGS1
RGS2
xmmsas_20070708_1801­7.1.0_CCF_prepub
Figure 5: The relative normalisations of the XMM instruments after joint fits to 118 bright AGN, using
the MOS QE CCF 0017.
6