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XMM-Newton Science Analysis System Page: 1
rgsbkgmodel
June 28, 2006
Abstract
Compute a model background spectrum from RGS background templates
1 Instruments/Modes
Instrument Mode
RGS Spectroscopy
2 Use
In the interactive environment.
pipeline processing no
interactive analysis yes
3 Description
The aim of this package is to compute a model spectrum of the RGS background applicable to a given
observation from a combination of observations of empty elds.
Two event les, one per RGS, were built merging 29 observations of empty elds with dierent levels of
background. Due their large size, these les were divided into 16 smaller event les per RGS according
to the value of the "Background Level Indicator", hereafter BLI, dened as the countrate of the o-axis
region of CCD9:
XDSP CORR < -3.E-4 rad OR XDSP CORR > 3.E-4 rad
which corresponds roughly to  1 arcmin from the on-axis position.
First and second order spectra were extracted from each event le. These spectra are the templates used
to derive the model background spectra.
First, the CCD9 o-axis light curve of the observation is computed. Then, the fraction of the light curve
within each of the 16 predened BLI levels is calculated, and the template spectra are combined weighted
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by these fractions. This weighted sum is the model background spectrum for the observation. No further
normalization is required.
The only restriction to the use of this task is the compatibility in the binning in beta of the input event
le and the templates event les. The latter have been processed with the 'rgsproc' defaults.
For more details on the procedure used to derive the templates, the denition of the BLI and some usage
examples, please see Ref. [1]
4 Parameters
This section documents the parameters recognized by this task (if any).
Parameter Mand Type Default Constraints
table yes table
specier
event list table speci-
er
A table specier which must point to a rgs event list table in a data set.
order no integer 1 1  integer  2
Re ection order to process.
pdistincl no real 90 0  real  100
Size of order regions, specied by the percentage of the pulse-height distribution covered between each
pair of vertices with the same dispersion coordinate.
backgroundmodelset no string Model background.ts valid le name
The name of the le to which the modeled background list is to be written.
5 Errors
This section documents warnings and errors generated by this task (if any). Note that warnings and
errors can also be generated in the SAS infrastructure libraries, in which case they would not be docu-
mented here. Refer to the index of all errors and warnings available in the HTML version of the SAS
documentation.
incompatible event le (error)
The input event le has beta channels value not equal to 3400.
No CCD 9 data (error)
The input event le has not got data in the CCD 9. The it is not possible to compute the
bkg model template
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6 Input Files
1. RGS event list le.
7 Output Files
1. Model background spectra (OGIP-compliant).
8 Algorithm
compute the background lightcurve of the problem event file applying
the following selection expression
CCDNR==9 AND (XDSP_CORR < -3.E-4 OR XDSP_CORR > 3.E-4)
From the lightcurve, calculate the fraction of the total time for
each of the pre-defined levels of background.
Compute the background template spectra by weighting each of the
template spectra by the corresponding factor calculated from the
ligthcurve.
9 Comments

References
[1] R. Gonzalez-Riestra. Templates for the RGS Background. Technical Re-
port XMM-SOC-CAL-TN-0058, XMM-SOC, October 2004. Found at the URL:
http://xmm.vilspa.esa.es/docs/documents/CAL-TN-0058-1-0.ps.gz.
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