Next: 5.6.1 Events, sources and selection criteria Up: 5 Analysis of RGS spectrometer data Previous: 5.5.1 Raw RGS Data Files in the ODF
The work done by rgsproc,
http://xmm-tools.cosmos.esa.int/external/sas/current/doc/rgsproc/index.html
falls into two main parts: first the construction of a calibrated event
list, and second the selection of events to be accumulated into spectra
for one or more of the entries in a source list. Event construction
starts from the spatial coordinates and pulse heights among the 6
columns of raw readout data stored in one file for each CCD and ends
with 17 calculated columns in one merged file for each RGS. A CCD
delivers a few hundred thousand events in a typical observation and the
merged file contains, therefore, perhaps a few million before event
selection begins. The final selected event file can contain less than
half of the merged events after exclusion of hot pixels and columns,
although after the RGS instruments were cooled in November 2002 the
hot stuff became much less numerous. Evidently, the rejection of hot
columns and pixels is a fundamental part of the analysis. The further
selection of events for source and background spectra then depends on
the position of the source within the RGS apertures as determined by
its coordinates held in the source list and the extent of the source and
background selection regions chosen explicitly or by default.
Here is an example rgsproc run on Mkn421 using accurate NED source coordinates in the directory scheme discussed above. As discussed in detail in § 2.3, the environment variables SAS_CCFPATH, SAS_ODF and SAS_CCF supply the SAS with calibration and data information so that rgsproc, which always writes its output files to the working directory, may be run in any location.
setenv SAS_CCFPATH /path/to/<CCF>
setenv SAS_CCF /path/to/<ODF>
setenv SAS_ODF /path/to/<ODF>
cifbuild
setenv SAS_CCF /path/to/<ODF>/ccf.cif
odfingest
setenv SAS_ODF /path/to/<ODF>/[rev]_[obsid]_SCX00000SUM.SAS
cd $SAS_ODF
mkdir RGS
cd RGS
rgsproc withsrc=yes srclabel=Mkn421 \
srcstyle=radec srcra=166.113808 srcdec=+38.208833
The task odfingest needs only to be run once after receipt of the ODF, while a new ccf.cif calibration index file should be regenerated with cifbuild whenever a new relevant CCF component is available. rgsproc has about a hundred potentially adjustable parameters, see http://xmm-tools.cosmos.esa.int/external/sas/current/doc/rgsproc/node26.html
In this case, the source coordinates only have been specified, leaving all other parameters at their default values, some of the more important of which are shown in Table 7.
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As it is running, rgsproc gives regular messages about its progress, although these are not designed to prompt any action except in the unlikely event of error. The final outcome, as shown in table 8, is a set of 16 FITS files for each RGS consisting of
and 3 other general-purpose FITS files. Source spectra are not background corrected by default so that the corresponding background spectra must explicitly be included in subsequent analysis with Xspec for example.
The RGS files have names of the form
If a file does not apply to a particular exposure, Sxxx is replaced by X000. Similarly, 0 and 000 show that the order and source number, respectively, are deemed irrelevant.
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