XMM-Newton Science Analysis System


evselect (evselect-3.71.2) [xmmsas_20230412_1735-21.0.0]

Event List Output

In addition to the above product files, the result of the filtering stage can be propagated into the output as well. This can be done in four different ways depending on the setting of the two task parameters flagcolumn and filteredset. The first parameter specifies the name of a column in the table which can be used to flag an event. In this non-destructive mode, non-selected events are merely flagged by setting a corresponding bit in the specified column, which must be integer-valued. The bit posistion to be manipulated must be set using the parameter flagbit. If the flagcolumn parameter is not set, non-selected events are physically removed, and thus will not be present in the final filtered event list. If non-destructive filtering is selected and the named flag-column does not exist, it will be created.

Thus setting of the filteredset parameter determines whether the input event list is modified according to the above two schemes or a new event list file is created accordingly. The following table provides a quick overview over the four possible cases:

	flag column not set	flag column set
output file name not set	the input file is modified; non-selected events will be removed	the input file is modified by adding an integer flag column indicating each event's selection status
output file name set	input file is not modified; selected events will be copied to new output file	input file is not modified; all events (selected and non-selected) get copied to new event list file with an integer flag column

If the filteredset parameter is not set, then the parameter keepfilteroutput, which is set to false by default, will prevent one from modifying the input table. If one wishes to modify the input file (either destructively or by flagging) one needs to set keepfilteroutput to true. Note that when evselect produces an output table file, it does so by first creating an exact copy of the input table file, and then preforming all filtering operations on the copy. Thus any extensions in the input file will also appear in the output file.