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

A.5. RATE FILES 71
Name Format [Units] Comment
TIME 1D [s] TIME associated with DPH
EXPOSURE 1D [s] Eposure of the histogram
DPH COUNTS (80,286,173)D [count] Detector plane histogram
DATA FLAGS 1I Data Quality 0=OK, 1=Problem
GAIN INDEX 1J Gain used in DPH
OFFSET INDEX 1J Offset used in DPH
LDPNAME 240A15 BAT LDP File Name
BLOCK MAP 1I Block Bit Mask
NUM DETS 1J Number of detectors
APID 1I Application ID
LDP 1I LDP product number
DPH COUNTS is a three-dimensional data cube with 80 × 286 × 173 elements. The first
dimension corresponds to the number of energy channels and can be varied, but will almost always
be 80 for BAT surveys. The second and third dimensions indicate the geometric location of the
detector in the BAT array plane. Since these dimensions include gaps between DMs, approximately
one third of the table is empty (filled with zeros).
The remaining columns are mostly for bookkeeping and trend analysis, but the data could be
filtered on some of these values.
The arrangement of data in the data cube was determined to maximize speed of filling the cubes
from the flight data products. A consequence is that the data cannot easily be visualized with tools
like fv. Two BAT tools, batdph2dpi and batdph2pha render the data cubes into, respectively, a
single Detector Plane Image or 32768 detector spectra. For science analysis and visualization,
batbinevt should be used.
The DPH FITS files also include an EBOUNDS extension specifying the energy bounds of the
histogram channels. There is also a GTI extension.
A.5 Rate Files
There are six types of rate files (light curves) produced by the BAT. Five of these are produced in
final form as Level 0 products. One of them (mask-tagged light curves) requires further processing
in the SDC pipeline using batmasktaglc.
The rate files are 1-second rates, quad rates, 64 msec rates, max rates, masktagged rates and
burst light curves. The first five types are produced at all times when the data ingest task is
running. The last type (burst light curve) is only produced in response to a burst. All rate files
have suffix “lc”.
A.5.1 One-second Rates
One-second rate files (code “rt1s”) are single channel light curves representing the total count rate
in the BAT array as a function of time (not background subtracted). Time binning is one second.
Since this file is derived from a hardware counter it continues to record the total BAT event rate
even when the data ingest task is turned off (during SAA passage, for instance) and includes all
events regardless of energy.
Name Format [Units] Comment
TIME 1D [s] TIME of Rates
COUNTS 1J [count] Array counts per 1 s bin