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Home > Data Analysis > XRT > pipeline

Producing cleaned XRT event-files

Level 2 cleaned event-lists (see the directory structure thread for an explanation of the different "levels" of data) are routinely generated by the SDC processing for the Quick Look site and archive. However, it is recommended that the users run the pipeline on the Level 1 files themselves, to ensure the most recent version of the processing scripts is being run or to change the level of filtering performed.

To run the pipeline, the command is simply xrtpipeline; however, other selections can be included on the command line to make subsequent analysis easier. For a full list of these, type plist xrtpipeline. Alternatively, fhelp xrtpipeline will reveal the help file, which could also be useful to read. Note that clobber=no is the default, so files will not be over-written.

Step-by-step

Here we use GRB 091029 as an example:

> xrtpipeline [createexpomap=yes cleanup=no] &> log
> Source RA position [ ] 60.17793
> Source DEC position [ ] -55.95425
> Target Archive Directory Path [ ] 00374210000
> Stem for FITS input files [ ] sw00374210000
> Directory for outputs [ ] 00374210000-xrt

Do not use spaces in the directory names (target archive or output).

Many files are created by the pipeline, with the most important one being the cleaned event-file (sw[obsid]x<mode><window><type>_cl.evt - see the files and directory structure thread for an explanation of the naming convention). We do not advise using the spectra automatically generated by xrtpipeline (which will be named sw[obsid]x<mode><window>posr.pha), since a default region size is used, with no attempt to check for pile-up; neither is any centroiding performed, with the region being centred exactly on the input coordinates.

Explanations

The commands within the square brackets are not required, but can be useful.

• createexpomap=yes creates an exposure map corresponding to each event-list; this is the default from version 3.7 of the software. See the exposure map thread for more details.
• cleanup = no keeps the temporary files created by the pipeline. Of most use are the region files centred on the position given, which will have names of the form sw[obsid]x<mode><window><type>.reg.
• The source RA and Dec can be given as decimal degrees (as in the example above) or as sexagesimal (hh mm ss.s). Alternatively, OBJECT or POINT can be given instead, in which case the relevant position will be obtained from the header of the event-list. (POINT will usually be different from OBJECT, since Swift performs offset pointings to try and avoid placing the sources over the bad columns.)
  The use of the actual source position is preferred for a number of reasons, including the alignment of multiple WT snapshots in the sky image and the PC mode bias correction. The position determination thread explains how to determine a position if the source coordinates are unknown.

The target directory path must include the auxil and xrt sub-directories.

Note that files produced by xrtpipeline cannot be written inside this target directory (that is, the directory of downloaded files - 00374210000 in the above example); the output directory must be at the same level or higher than the input one in the directory structure. As mentioned above, directory paths should not include spaces: /home/GRB091029 would be acceptable, but /home/ GRB 091029 would not, for example.

The stem for the input files is always sw followed by the 11 digit concatenation of the target ID (8 digits) and observation segment number (3 digits).

Attitude files

As explained here, there are three different types of Swift attitude file. You can determine which has been used when running xrtpipeline by looking at the ATTFLAG keyword in the EVENTS extension of the event list. The flags are defined as:

• 100 = sat file
• 110 = pat file
• 111 = uat file

This same attitude file (be it sat, pat or uat) should be used when creating exposure maps and running xrtlccorr.

Additional Information

For version 2.8 and later of the Swift software, the default screening criteria (for data collected since September 2007) are:

 (ELV>=28||BR_EARTH>=120)&&(SUN_ANGLE>=45&&ANG_DIST<=0.15&&MOON_ANGLE>=14)&&
((CCDTemp>=-102&&CCDTemp<=-47)&&(Vod1>=29.8&&Vod1<=30.25)&&(Vod2>=29.30
 &&Vod2<=29.80)&&(Vrd1>=16.40&&Vrd1<=16.80)&&(Vrd2>=16.45&&Vrd2<=16.90)&&
(Vsub>=5.67&&Vsub<=6.07)&&(Vbackjun>=5.65&&Vbackjun<=6.05)&&(BaseLin1>=0.1&&
BaseLin1<=0.4)&&(BaseLin2>=-0.1&&BaseLin2<=0.1))&&((STAST_LOSSFCN>=0&&
STAST_LOSSFCN<=5.0E-9)||(STAST_LOSSFCN>=1&&STAST_LOSSFCN<=1.0E+3))&&(STLOCKFL==1)
&&((SETTLED==1&&TEN_ARCMIN==1)||(SETTLED==1&&TEN_ARCMIN==0&&SAFEHOLD==0))

Note that the substrate voltage (Vsub) was raised from 0V to 6V on 7th August 2007. Previous data are (automatically) processed with Vsub>=-0.1&&Vsub<=0.1&&Vbackjun>=-0.1&&Vbackjun<=0.1

The default CCD temperatures should, in general, be acceptable. However, should the observation be particularly hot, and the data are still required, a GTI expression needs to be included; i.e.:

xrtpipeline gtiexpr="<required expression>"

where the <required expression> is a list of boolean commands. As an example, to remove all temperature and angular filtering, simply typing xrtpipeline gtiexpr="SAA==0" would work. See xrtscreen for more details.

Please note that, if you include a GTI expression, the only additional filtering which will be done by default will be (SETTLED==1&&TEN_ARCMIN==1)||(SETTLED==1&&TEN_ARCMIN==0&&SAFEHOLD==0). Any filtering on the star trackers will be lost unless explictly stated in the gtiexpr input.