Xselect supports region and timing filters, as well as pha upper and lower bounds. These filters are not immediately applied, but stored and used in the next run of the extract command.
The filters are entered with the commands
xsel > filter time
xsel > filter region
xsel > filter pha_cutoff
The timing filters can be entered in any of three formats, ASCII, or FITS GTI files, with start and stop columns, and Xronos window format files. Timing filters can be entered graphically using the plot curve command, after a light curve has been made. These filters will be automatically applied, you do not need to enter them with the filter time command.
The region filter is in SAOImage format. Region filters for the filter region command can be created graphically via the plot image command, which spawns an SAOIMAGE session. However the resultant regions have to be read back into Xselect with the filter region command.
At this point, only a lower and upper cutoff for the PHA are allowed.
There are a few other filters created within Xselect which are automatically entered into the extract command. These are the GTI files created by the select mkf, and the select event commands, and the region files created by the sisclean command.
The filters that have been entered can be listed by the command
xsel > show filter
They can also be cleared by the various clear commands (see clear under the Commands subheading)
xsel > clear region
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