Task epreject is intended to be run immediately after task epframes, either in the PPS or alternatively as part of the offline analysis using the epchain script. Noise events flagged by epreject may be physically removed from the event list, considerably reducing the file size of the event set. The epchain task parameters runepreject, sigma, badcolumnset, noiseparameters, and screenrejected are available to control the behavior of epreject and the subsequent event filtering. Care should be taken that parameter screenlowthresh is set to a sufficiently low value (120 eV) to preserve the noise-screened low energy events in the final calibrated event set. A typical epchain call to run epreject would look like this (see epchain task description for other epchain parameters):
epchain runepreject=yes screenrejected=yes screenlowthresh=120 ...
After running epchain, a noise screened low energy image may, e.g., be created by the following call
evselect expression='PHA>20 && PI in (120:200)' ...
Note, that events with PHA values below 20 need to be removed to create a clean image.
Sometimes offset maps are not available within the ODF/SDF – they may be been dumped instead in the observation before or after the one to be processed, with different ObsID. A work-around is implemented for epreject via an ASCII list of corresponding offset maps outside the ODF/SDF.
This is controlled via the parameter withoffsetlist (default “N”) that takes precedence over parameter withoffsetmap if set to “Y”: it opens the file specified in parameter odilist and reads the ODI name to be used from there. The input list is an ASCII with 2-digit CCD number followed by a blank and then the path to the offset map for that CCD (there can be more than one offset map in that file so that the input file can be used for the whole observation processing in epchain; only the first entry for a particular CCD is used; the order does not matter).
An example input file (you may call it 2462_9246200004_PNS00300ODI.ASC) useful for slew 9246200004 is listed below:
01 /xmm/public/data/2462/0723780401/2462_0723780401_PNU40101ODI.FIT 02 /xmm/public/data/2462/0723780401/2462_0723780401_PNU40102ODI.FIT 03 /xmm/public/data/2462/0723780401/2462_0723780401_PNU40103ODI.FIT 04 /xmm/public/data/2462/0723780401/2462_0723780401_PNU40104ODI.FIT 05 /xmm/public/data/2462/0723780401/2462_0723780401_PNU40105ODI.FIT 06 /xmm/public/data/2462/0723780401/2462_0723780401_PNU40106ODI.FIT 07 /xmm/public/data/2462/0723780401/2462_0723780401_PNU40107ODI.FIT 08 /xmm/public/data/2462/0723780401/2462_0723780401_PNU40108ODI.FIT 09 /xmm/public/data/2462/0723780401/2462_0723780401_PNU40109ODI.FIT 10 /xmm/public/data/2462/0723780401/2462_0723780401_PNU40110ODI.FIT 11 /xmm/public/data/2462/0723780401/2462_0723780401_PNU40111ODI.FIT 12 /xmm/public/data/2462/0723780401/2462_0723780401_PNU40112ODI.FIT
