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

D.1. BATBINEVT 95
batbinevt can also output histograms and images:
DPH detector plane histogram; for each temporal integration, a three dimensional histogram of
the number of counts is constructed with two spatial dimensions (DETX and DETY) and
one energy dimension. batbinevt can rebin an existing DPH in time or energy, or generate a
new DPH from event data. The EBOUNDS extension describes the energy binning. (default:
weighted=no, outunits=COUNTS);
DPI detector plane image; a histogram of the number of counts in two spatial dimensions (DETX
and DETY). Each FITS extension contains only one DPI; multiple images are stored in
concatenated FITS extensions. batbinevt can either “flatten” existing DPHs into DPIs, or
make new DPIs from event data. (default: weighted=no, outunits=COUNTS);
DPITAB detector plane image. Images are stored in rows of a FITS binary table (multiple
images in one extension). (default: weighted=no, outunits=COUNTS).
WEIGHTED or UNWEIGHTED?
Applying mask weighting is equivalent to background subtraction. Detectors which are fully shadowed
are assigned a -1 weight, and fully illuminated detectors a +1 weight, and partially illuminated
detectors are assigned an prorated value. Thus, a weighted sum of the counts will automatically
subtract the background.
The default of the ‘weighted’ parameter depends on the output type.
• light curves and spectra are weighted by default;
• histograms and detector images are not weighted by default.
Users can choose to change the default by setting weighted to “yes” or “no.”
For event data, the default is to take the mask weighting values for each event from the
MASK WEIGHT column. This can be overridden by using the maskwt parameter, which gives
a mask weight map to be used for all events. [This parameter should not be used for event data
taken during slews.] For DPHs, the mask weighting is also specified using the maskwt parameter.
TIME BINNING
The user can choose how to bin the data in time. For “uniform” binning, a non-zero time bin size
indicates that every time bin should have the same size. A zero time bin size indicates that all
input data should be summed into a single output time bin.
For “gti” binning, the user specifies the desired bins using the gtifile parameter, which is in
the standard GTI format. Adjoining good time intervals are not merged when using this method.
The timedel bin size is ignored. Note that the ‘minfracexp’ parameter is always honored. If it is
important to preserve all requested bins, even if they have zero exposure, then set minfracexp=0.
For “snr” binning, the user specifies a desired signal-to-noise ratio with the snrthresh parameter.
When the total signal to noise ratio for a given time bin exceeds the threshold, a new bin is started.
The timedel bin size is taken as the maximum bin size before a new bin is started; if timedel=0
then there is no maximum.
The “infile” binning method only applies when the input is a DPH. When the binning algorithm
is set to “infile,” then the time binning of the input file is preserved in the output file. This may