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

38 CHAPTER 5. BAT ANALYSIS PROCEDURES
cd 00145675000/bat/event
If the event file is compressed, unzip it. The mask-weighting task modifies the event file in
place, and gzipped files cannot be modified.
gunzip sw*.evt.gz
5.5.5 Compute Mask Weights for BAT Events
The mask-weighting task for events is called ‘batmaskwtevt’. Here is an example run,
batmaskwtevt infile=sw00145675000bevshsp_uf.evt \
attitude=../../auxil/sw00145675000sat.fits.gz \
ra=320.5397083 dec=+77.074861 \
detmask=../hk/sw00145675000bcbdq.hk.gz \
rebalance=YES corrections=default \
auxfile=/local/data/gcn5b/craigm/sw00145675000bevtr.fits clobber=YES
• infile gives the event file name
• attitude gives the attitude file name
• ra and dec give the revised sky position of the GRB (see above)
• detmask is a quality filter which excludes disabled and noisy detectors; this is important so
than an accurate accounting of the number of illuminated detectors can be computed
• rebalance=YES means that the resulting light curves will be background-subtracted
• corrections=default applies the default corrections to the mask weights
• auxfile gives the output auxiliary raytracing file, to be used for spectral analysis
This analysis may take some time (several minutes), as each event needs to be ray-traced. The
speed of the task depends on the number of slews that occur during the observation (i.e. more
slews require more intensive calculations).
5.6 Light Curve from Event Data
This section describes how to generate a light curve from BAT event data. Later sub-sections
describe how to make a light curve with custom time binning.
Figure 5.2 shows schematically how light curves are created using the batbinevt task. The same
task is used to create spectra and detector plane images and detector plane histograms.
5.6.1 Prerequisites
• BAT event data (in obsid/bat/event/swNNNNNNNNNNNbevshsp uf.evt.gz);
• BAT quality map (in obsid/bat/hk/swNNNNNNNNNNNbcbdq.hk.gz).