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XMM­Newton CCF Release Note
XMM­CCF­REL­250
RGS Background Spectra Templates
R. Gonz’alez­Riestra
March 12, 2009
1 CCF components
Name of CCF VALDATE EVALDATE Blocks changed XSCS flag
RGS2 TEMPLATEBCKGND 0006 2007­08­17T00:00:00 -- X100 P090 1 0.00... NO
X100 P095 2 8.00
2 Changes
This release of the RGS background spectra templates applies only to RGS2.
The update of this CCF was required due to the implementation of the single­node readout
mode for RGS2. This mode started to be used in routine operations in revolution 1408 (August
17 2007), due to the increasing frequency of the RGS2 ADC anomaly. The change in some of the
characteristics of the RGS2 CCDs after switching to this mode made necessary to revise this CCF.
The template corresponding to each of the 16 background levels is the average of the spectra
extracted for that given level from 16 blank fields taken in the period September 2007 ­ May 2008.
These background template spectra have been extracted with version 2.6.3 of the SAS task
rgsspectrum. The procedure followed to derive the templates is detailed in the Appendix.
The structure of the calibration file remains as it was in the previous release (see [1]): the file has
64 extensions, 32 for first­order and 32 for second­order background spectra. The first 32 extensions
in the file correspond to an extraction region of 90% in PI (16 for first order, 16 for second order).
The last 32 extensions correspond to an extraction region of 95% in PI (16 for first order, 16 for
second order).
1

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Figure 1: RGS2 event files corresponding to two observations taken in double­node (top) and single­
node (bottom) readout mode. Only CCDs 3, 2 and 1 (from left to right) are shown.
3 Scientific Impact of this Update
Shortly after the implementation of the single­node readout mode for RGS2, it was noticed that the
background characteristics of the RGS2 CCDs (in particular, CCD#2) had changed: the background
was lower, and the fixed­pattern noise had nearly disappeared (see Fig. 1). Due to these changes,
the background templates derived from double­readout mode observations overestimated largely the
background at the longest wavelengths (Fig. 2).
The background derived from this new CCF shows a substantial improvement, in particular in
the wavelength interval between 28 and 33 š A, that corresponds to CCD#2 of RGS2 (see Fig. 2).

XMM­Newton CCF Release XMM­CCF­REL­250 Page: 3
Figure 2: Comparison of the RGS2 background templates derived from the old (red) and new (blue)
CCFs. The figure shows the RGS2 spectrum of the galaxy cluster Abell 1413 obtained in November
2007, that was taken in single­node readout mode. The black line is the total spectrum, as extracted
with rgsspectrum without background subtraction. The red and the blue lines are the resulting
model background computed using CCFs 004 (double­node readout) and 005 (single­node readout),
respectively. The improvement in the estimation of the background in the spectral region 28­33 š A
is clearly visible.

XMM­Newton CCF Release XMM­CCF­REL­250 Page: 4
4 Expected Updates
Further updates might be made in the future to improve the signal­to­noise ratio of the templates
by adding more blank fields and/or to cope with software updates.
5 Test Procedures and Results
The new templates have been used to generate the model background for a sample of RGS2 obser­
vations taken in single­node readout mode. The sample included di#erent levels of background, first
and second orders, and 90 and 95% PI extraction regions. The results were satisfactory in all cases.
Formal checks:
. The fits viewer fv was used to inspect the CCF file, their structure and validity dates. Ev­
erything was OK: It contains 64 binary extensions, each with five columns: CHANNEL, RATE,
QUALITY, BACKSCAL and AREASCAL.
. The SAS task cifbuild was run successfully in order to check the ingestion of the files into
the calibration index file.
References
[1] ``RGS Background Spectra Templates'' R. Gonz’alez­Riestra, XMM­CCF­REL­217, June 2006
[2] ``Templates for the RGS Background'', R. Gonz’alez­Riestra, XMM­SOC­CAL­TN­0058, October
2004
Appendix
The RGS2 observations listed in Table 1, corresponding to blank fields taken is single­node readout
mode, were selected for the extraction of the background templates specific for this observing mode.
All the observations were processed with SAS 8.1 following the procedure detailed in [2].
For each of these observations, spectra were extracted for the standard 16 background levels as
defined in [2]. The spectra for each of the levels were added together. This was done for first and
second orders, and for PI extraction regions of 90 and 95%. No valid data were found for the three
highest background levels (i.e. BLI > 4 cts/sec). For compatibility with previous releases, dummy
files were created for these three levels, having the same values as the last valid file (that corresponds
to 2 
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Table 1: Sample of observations
Obsid Target Date Texp (sec)
05002401 V838 Mon 2008­03­17 116803
05003001 G330.2+1.0 2008­03­20 68249
05005009 PG 2112+059 2007­11­05 51456
05021401 SGR 1627­41 2008­02­12 90722
05024302 RX J0957.8+6534 2007­09­30 58464
05024303 RX J2328.8+1453 2007­12­01 10439
05025001 3C 457 2007­12­02 52785
05027601 B2 0902+343 2008­04­09 55570
05028601 CL 0016+1609 o#set 2007­12­14 61448
05029501 CL 2038.4­0125 2007­11­07 52759
05029502 CL 0035.9+8513 2008­02­11 61575
05037401 IRDC G053.11+00.05 2008­03­29 54793
05040101 vb 10 2008­04­06 47703
05054001 PHL 1092 2008­01­20 63565
05059201 PSR J1856+0245 2008­03­27 53961
05523501 MGRO J2019+37 2008­05­08 47983
Table 2: Characteristics of the background templates
BLI # n Texp(sec) counts rate (cts/sec)
# 0.01 8 33921 3568 0.077±0.006
0.01 < BLI # 0.02 13 74950 6274 0.078±0.005
0.02 < BLI # 0.04 16 240188 19726 0.083±0.006
0.04 < BLI # 0.06 16 194077 16705 0.086±0.004
0.06 < BLI # 0.08 16 90387 8332 0.092±0.003
0.08 < BLI # 0.10 9 32528 4543 0.105±0.008
0.10 < BLI # 0.20 13 77491 11220 0.142±0.016
0.20 < BLI # 0.40 13 72382 17125 0.241±0.032
0.40 < BLI # 0.60 12 41563 16296 0.398±0.045
0.60 < BLI # 0.80 12 25285 13754 0.550±0.099
0.80 < BLI # 1.00 11 18891 12681 0.688±0.100
1.00 < BLI # 2.00 11 41309 44120 0.980±0.217
2.00 < BLI # 4.00 4 6927 11652 1.681±0.240
4.00 < BLI # 6.00 0 ­ ­ ­
8.00 < BLI # 8.00 0 ­ ­ ­
BLI > 8.00 0 ­ ­ ­
# BLI: countrate in the o#­axis region of CCD#9 (see [2])
n: number of spectra
Texp: accumulated exposure time in the level
counts: number of counts in the accumulated spectrum. They correspond to first order and an
extraction region of 95% in PI