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

66 CHAPTER 6. BAT ANALYSIS ISSUES
6.3.10 batbinevt: Incorrect exposure for survey analysis
Task: batbinevt
Version: 1.13 and earlier
What Builds: Swift 2.0 and earlier
Problem: EXPOSURE keyword can be incorrect for survey analysis
Status: Closed Swift 2.1
Updated: 20 Jul 2005
batbinevt can apply a user-specified good time interval (GTI) file, or by specifying tstart/tstop
on the command line.
If either of these time selections cuts through the middle of a survey histogram (DPH), then
what should happen is that DPH is excluded from analysis. What actually happens is somewhat
complicated, and may result in an incorrect EXPOSURE keyword value being computed (the same
is true for the GTI extension).
This bug has been fixed for Swift 2.1.
6.3.11 CALDB: Incorrect Spectral Response < 20 keV
Task: CALDB
Version: 20030101 version 2 and 20041006 version 1
What Builds: Swift 1.3 and earlier
Problem: Pre-launch response over-estimates effective area below 20 keV
Status: Closed Swift 2.0
The pre-launch BAT spectral response file has significant systematic errors below 20 keV. This
are caused primarily by the model of passive absorbing material in the BAT field of view. The
errors were 30-50% in the 15-20 keV band.
The response matrix has been improved significantly for builds 12 and 14. Users should retrieve
the newest set of CALDB files at the same time as downloading new software (at least Swift 2.0
and the corresponding CALDB release).
Users should be aware that significant systematic errors remain even after these adjustments,
so they should apply a systematic error vector to all spectra.
6.3.12 CALDB: Incorrect Alignment Matrix
Task: CALDB
Version: 20041013 and earlier
What Builds: Swift 1.0 and earlier
Problem: Pre-launch alignment matrix leads to incorrect positions and fluxes
Status: Fixed in Swift 1.1
The BAT alignment matrix components are composed of two files: the “TELDEF” file which
describes the alignment of the BAT boresite with respect to the spacecraft, and the “aperture” file
which describes the alignment of the mask with respect to the detector array.
These files were checked into CALDB with their pre-launch best guess values. They were further
refined after launch according to the calibration plan, and using serendipitously detected sources
with known positions.
Users of the pre-launch matrix will find the following problems: