The nicermergeclean task is a high-level task that merges data from multiple NICER MPU slices, and applies standard screening. It is equivalent to running the tasks nimpumerge (for merging MPU data) and nicerclean (for applying screening).
An input to the task is a set of several MPU event files, which have been calibrated but not finely screened. These are typically named niNNNNNNNNNN_0mpuN_ufa.evt, where the "ufa" indicates unscreened but calibrated data. The output of the task is a single merged and screened event file, which is typically named niNNNNNNNNNN_0mpu7_cl.evt, where the "cl" indicates a cleaned event file. Here "mpu7" means all MPUs, numbered 0-6, have been merged into one file designated as "mpu7."
Another input to the task is a GTI (good time interval) file which contains the desired screening good time intervals. Note that nicermergeclean does not by itself create a GTI file, but rather uses one created externally by the user. The NICER team recommends to use nimaketime first to accomplish this, before running nicermergeclean.
This task runs the following lower-level NICER tasks to complete its work.
In addition to applying good time screening, the nicerclean task also applies per-event screening based on event type and pulse height range. See the documentation for nicerclean for more information.
By default, events with pulse invariant (PI) pulse heights above 20 (i.e. 200 eV and above). This can be changed using the pirange parameter. For example, use pirange=35:1000 to select events with nominal pulse heights in the range 0.35 - 10.00 keV.
When trumpetfilt=YES, nicermergeclean performs standard filtering to exclude background events using the event PI_RATIO column. This is known as "trumpet" filtering since the PI vs PI_RATIO cloud looks like a trumpet. See nicerclean for more information.
Merge and clean an event file.
nicercal indir=1706221428 outdir='$INDIR/xti/event_cl' \ outfilefile=ufalist.lis nimaketime infile=1706221428/auxil/ni1706221428.mkf \ outfile=standard.gti nicermergeclean email@example.com \ ufafile=1706221428/xti/event_cl/ni1706221428_0mpu7_ufa.evt \ clfile=1706221428/xti/event_cl/ni1706221428_0mpu7_cl.evt \ gtifile=standard.gti
The first two commands are calls to the tasks nicercal and nimaketime. The output of nicercal is a set of calibrated files in the event_cl directory. nicercal also produces an inventory of the files it created, here named ufalist.lis. This file is used as input to nimergeclean. Note that you can also use 'ls' with a wildcard match to find the relevant files, such as
ls 1706221428/xti/event_cl/ni*_0mpu[0-6]_ufa.evt > ufafiles.lis
The nimaketime call produces a good time file called standard.gti. This is also used as input to nimergeclean.
Finally, the call to nicermergeclean is used to combine the calibrated files into a single file and apply the good time filtering GTI file produced by nimaketime.
nicercal, nimpucal, nimaketime, nicerclean