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 behaviour 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.