The SWIFT BAT Software Guide Version 6.3 30 ... - HEASARC - Nasa

5.6. LIGHT CURVE FROM EVENT DATA 41
An easy way to make light-curves in multiple bands is to re-run the task with different energy
ranges. For example, if you want to make light curves in the 15-50 and 50-150 keV bands, you can
run the task twice:
batbinevt ... energybins=15-50 ...
batbinevt ... energybins=50-150 ...
This will produce two light curve files, each with the different energy ranges.
Another way to make multi-channel light curves is to specify both energybins in one command.
In the example above of two bands (15-50 and 50-150 keV), the command would be:
batbinevt ... energybins=15-50,50-150 ...
This will produce one light curve file with a vector RATE column. You can plot these within
‘fv’ using RATE[1] and RATE[2] as the Y column names.
5.6.6 Changing the time binning
The task ‘batbinevt’ has several options for time binning of light curves.
• uniform time binning (timebinalg=‘u’) - you choose the time bin size with the timedel
parameter, or set it to zero to sum all the data into one bin;
• constant signal to noise (timebinalg=‘s’) - the time bin size is variable and determined by
the signal to noise ratio of the data (using the snrthresh parameter);
• user-specified binning (timebinalg=‘g’) - you explicitly set the time bin edges using the
gtifile parameter.
The user-specified binning gives you the freedom to choose precisely the time bin edges that you
wish (expressed in mission elapsed time). You specify these bin edges with a good time interval file
(GTI file). The task ‘battblocks’ can produce a set of “interesting” time bins automatically using
the Bayesian block algorithm. You can also construct a GTI file by hand (see below).
5.6.7 Optional: Making a GTI file
This example shows how to make a GTI file with user-specified time bins. We will assume the time
bins of interest are already known relative to the trigger time. The goal will be to make a GTI file
with absolute mission elapsed times.
For example, enter the time bin edges in the text file gti.txt. These are in seconds relative to
the trigger time. Of course you can choose any relative times that you wish.
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