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

5.9. DETECTING SOURCES IN BAT IMAGES 51
• detecting a source blindly
• detecting a source at a known position
5.9.2 Prerequisites
We will practice the operation image data from on GRB 050713A (obsid 00145675 000).
Here is what is needed:
• BAT sky image (say, preslew.img)
• partial coding map (say, preslew.pcodeimg)
For example, we use the documentation on “Making BAT Sky Images” to create sky images
and partial coding maps. These kinds of images can also be generated using the ‘batgrbproduct’
task, which creates a complete set of analysis products for a gamma-ray burst. The Swift Data
Center also makes BAT sky images as a part of its standard processing.
5.9.3 Perform Blind Source Detection
batcelldetect operates on a sky image and partial coding map to produce a catalog of detected
sources.
Issue the following command,
batcelldetect preslew.img preslew.cat 5 \
pcodefile=preslew.pcodeimg regionfile=preslew.reg \
clobber=YES
where
• preslew.img is the sky image
• preslew.cat is the output catalog produced by batcelldetect
• “5” is the local signal to noise detection threshold in sigma units (this should always be at
least 4)
• pcodefile is the partial coding file
• regionfile is a region file produced by batcelldetect which you can load into an image viewer
like DS9
• clobber=YES is usually recommended, since otherwise batcelldetect may attempt to append
to an existing catalog file.
The Output
The output of the task should look something like this (for the prompt pre-slew emission of this
particular GRB):