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

D.13. BATMASKTAGLC 157
D.13 BATMASKTAGLC
D.13.1 NAME
batmasktaglc - Compute background subtracted light curves from raw BAT mask tagged counts
D.13.2 USAGE
batmasktaglc infile quadfile maskwt outfile [detmask] [ebounds]
D.13.3 DESCRIPTION
batmasktaglc converts a raw “mask tagged” light curve, produced by the BAT flight software, into
a background subtracted mask weighted light curve. The BAT flight software by itself produces
“unbalanced” mask weighted sums, which introduces a bias. This task must be used to remove the
bias.
The three basic inputs to the task are the raw mask tagged light curve; the “quadrant rates”
light curve; and the mask weight map used by the flight software to create the raw mask tagged
light curves.
Generally speaking, raw mask tagged light curves will be stored with file names like: swNNNNNNNNNNNbmtCC
where NNNNNNNN is the observation and segment numbers, andCCCCCCCC is the bat catalog
number for the source. A given observation may contain multiple mask tagged sources. The
BAT can produce mask tagged light curves for up to three sources simultaneously. In addition,
the sources chosen for mask tagging may vary from pointing to pointing in the same observation.
Gamma-ray burst mask tagged light curves will have a catalog number of the form, 0002CCCC,
where CCCC matches the last four digits of the GRB trigger number in decimal.
The quadrant rates file is typically in the obsid/bat/rate directory, with a file name, swNNNNNNNNNNNbrtqd.lc
It contains the total rates in each quadrant of the instrument, in several energy bands.
A mask weight map is produced by the BAT every time the mask tagged sources change
(typically every pointing), and describes the weighting each detector had in computing the mask
tagged sums. Typically, the maps should be attached to the raw mask tagged light curve file as
follow-on extensions. Thus, users should normally just set “maskwt=INFILE”. The extension name
of the weight map should be “MASK TAG WEIGHT”.
The tool basically backs out the light curve processing that was carried out in the flight code to
derive a background subtracted light curve and appropriate statistical error bars. The output file
is a standard light curve file, containing TIME, RATE, ERROR and BACKGROUND columns,
each entry of which is a four-dimensional vector, with one number for each of the energy ranges
described in the EBOUNDS extension.