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

5.5. MASK WEIGHTING (RAY TRACING) 37
Checking for old software versions
The SDC has used several versions of the software throughout the mission life-time, and they are
not always the best versions. Versions of the software before HEASOFT 6.0.3 contained an error
which affects the flux determination of far off-axis bursts. HEASOFT 6.1.2 introduced some new
filtering techniques which should slightly improve sensitivity. You can check which version of the
software was used with the following command:
fkeyprint sw00145675000bevshsp_uf.evt.gz BATCREAT
You should see the following result:
# EXTENSION: 1
BATCREAT= ’batmaskwtevt 1.11’ / BAT Program that modified this FITS file
If you see a version earlier than 1.11, then you should definitely re-run the mask-weighting task.
If you see a version earlier than 1.16, then you might consider re-running the mask weighting task,
which could gain a slight improvement in sensitivity.
What is an auxiliary raytracing file?
An auxiliary raytracing file contains information about the position of the GRB and the mask
geometry as a function of time within the BAT field of view. This information is needed to make
an accurate spectral response before, during and after the spacecraft is slewing to the burst. As
of late 2005, the SDC has started to make an auxiliary raytracing file for each observation. Before
that time, the file will not be present, and you will need to re-run the mask-weighting tool in order
to produce one.
5.5.3 Prerequisites
We will practice the mask weighting on GRB 050713A (obsid 00145675 000).
Here is what is needed:
• Known position of the GRB (RA and Dec)
• Attitude file (obsid/aux/swNNNNNNNNNNNsat.fits.gz)
• BAT event data (in obsid/bat/event/swNNNNNNNNNNNbevshsp uf.evt.gz);
• BAT quality map (in obsid/bat/hk/swNNNNNNNNNNNbcbdq.hk.gz)
In this case, let us enter the revised position as reported by Castro-Tirado (GCN 3584):
RA=320.5397083, Dec=+77.074861, and apply the mask weighting operation to the original event
list.
5.5.4 Initial Steps
Change directories to the location of the event data.