Документ взят из кэша поисковой машины. Адрес оригинального документа : http://xmm.vilspa.esa.es/docs/documents/CAL-SRN-0179-1-1.ps.gz Дата изменения: Fri Oct 15 17:35:00 2004 Дата индексирования: Mon Oct 1 22:30:26 2012 Кодировка: Поисковые слова: star trail

XMM-Newton CCF Release Note
XMM-CCF-REL-179
RGS Background Spectra Templates
C. Gabriel
October 15, 2004
1 CCF components
Name of CCF VALDATE EVALDATE Blocks changed XSCS ag
RGS1 TEMPLATEBCKGND 0001 2000-01-01T00:00:00 { { NO
RGS2 TEMPLATEBCKGND 0001 2000-01-01T00:00:00 { { NO
2 Changes
This is the rst release of the RGS background spectra templates CCFs. These calibration les
contain each 16 extensions for rst and 16 extensions for second order background spectra. They
correspond to the rst and second order spectra derived from RGS blank elds within each of the
16 dened levels of background. The levels are measured by the count rate in a dened oset region
of CCD 9. The whole method is explained in XMM-SOC-CAL-TN-0058 by Rosario Gonzalez, who
developed this alternative for RGS background derivation.
3 Scientic Impact of this Update
The use of the background spectra templates is an alternative to the conventional analysis, in
which the background is derived from the oset region in the spatial image. This new method of
determining the background is especially important for analysing:
 extended objects leaving less or no background regions in the RGS spatial image,
 weak sources, by which an improvement of the signal to noise ratio could be essential.
1

XMM-Newton CCF Release XMM-CCF-REL-179 Page: 2
4 Estimated Scientic Quality
With the exception of pathological cases (less than a few percent) the establishment of the overall
background spectrum in an observation using the background spectra templates (as done by the
SAS task "rgsbkgmodel") works very well, constituting a valid alternative for ANY observation, and
the ONLY one for largely extended sources. A very good reproduction of the background obtained
with the conventional analysis could be achieved in all the control cases tested so far, using dierent
types of objects with dierent levels of background.
5 Expected Updates
The derivation of the background spectra was performed using all the data available from the rst
700 XMM-Newton orbits. No signicant updates can be therefore expected before several years.
6 Test procedures
General checks:
 use FV (or another ts viewer) for le inspection. It should contain 32 binary extensions
 use the SAS task cifbuild to see if the CAL digests and creates correctly the calibration index
le.
7 Summary of the test results
Initial quality check:
Tests were run on ca. 1500 observations, comparing the results obtained using the new SAS task
rgsbkgmodel (which uses this set of CCFs) versus the results obtained with the prototyped IDL
procedures. The results were identical, within the rounding accuracies.
A full description of the method and results obtained, also using even these CCF les with the
new SAS task rgsbkgmodel (to be released with SAS 6.1) is given in the Calibration Technical Note
XMM-SOC-CAL-TN-0058 "Templates for the RGS Background" [1].
General checks:
The ts viewer fv was used to inspect the two CCF les, wrt their structure and validity dates.
Everything OK.

XMM-Newton CCF Release XMM-CCF-REL-179 Page: 3
The SAS task cifbuild was run succesfully in order to check the ingestion of the les into the
calibration index le.
References
[1] "Templates for the RGS Background", R. Gonzalez-Riestra, XMM-SOC-CAL-TN-0058, October
2004