XMM-Newton Science Analysis System: User Guide

4.3.1 Running the EPIC MOS processing meta-task

A description of the functional organigram for the EPIC MOS processing is given in figures 6 and 7. The emproc meta task concatenates all first-level EPIC MOS tasks to produce calibrated event lists for all selected exposures.

The main subroutine (figure 6) loops over all selected exposures and instruments (MOS1/MOS2) present in the input directory. It creates one (or two, if a CCD is operated in TIMING mode) event list for a single exposure, from all relevant ODF material and (if they exist) the good time intervals generated by tabgtigen and the list of bad pixels (from the CCF or produced internally). In a first step (figure 7) it loops over all CCD/nodes, calling in sequence:

1. emframes on the auxiliary file, the event file and the external GTI file (if any), creating a frame file as expected by emevents and a CCD/node specific GTI file which will be re injected in the final call to evselect.
2. badpix on the event list, adding the BADPIX extension. If a bad pixels file exists, it is used instead of the CAL calls for the non-uplinked bad pixels.
3. emevents on the event list, the offset/variance file and the frame file, creating a new event list which will be propagated through attcalc and emenergy to evlistcomb.
4. gtialign on the external GTI file and the event file, then the task gtimerge to merge the resulting aligned GTI and the CCD/node specific GTI.
5. attcalc on the new event list, filling the X/Y columns.
6. emenergy on the new event list, filling the FLAG, PHA and PI columns.

Then evselect is called on the resulting event list(s) applying (by default) the destructive filter selection (#XMMEA_EM) && (FLAG & 0x762a0000) == 0. Note that in case of emchain, (#XMMEA_EM) is not applied: here events flagged as OUT_OF_FOV and REJECTED_BY_GATTI are kept in the list (as they are useful for background assessments and flare screening, respectively). For a description of the event attribute based selection, refer to the documentation of the SAS package evatt.

All the event list files created (one per CCD/node) are merged by evlistcomb, creating one event list per mode (IMAGING, TIMING). Finally evselect is called on the resulting events list(s), with (CCDNR == $node$ccd) && GTI(merged GTI file,TIME) for all CCD/nodes.

In the EPIC MOS imaging mode, the EVENTS binary table of the calibrated event list file contain 12 columns i.e TIME, RAWX, RAWY, DETX, DETY, X, Y, PHA, PI, FLAG, PATTERN and CCDNR. DETX and DETY are the event position in the focal plane array. X and Y are the event position in sky coordinates. PHA is the pulse analyser channel and PI the pulse independent channel. CCDNR is the CCD number. For a description of the FLAG column, see the documentation of the SAS package evatt. The PATTERN definition is given in the documentation of the task emevents (see also figure 12).

In the EPIC MOS timing mode, the EVENTS binary table of the calibrated event list file contains only 7 columns: the spatial coordinates RAWY, DETX, DETY, X, Y are not present as (in this mode) only one axis (RAWX) contains spatial information whereas the other axis is a measure of the arrival time of the event.

Figure 6: Organisation of the EPIC MOS chain: merging the event lists. The files in boldly dashed boxes are used (or produced) if they exist. The files in simply dashed boxes are options of the individual tasks not used in the current chain.

Figure 7: Organisation of the EPIC MOS chain at CCD/node level with file inputs. Same conventions as in figure 6.