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

68 CHAPTER 6. BAT ANALYSIS ISSUES
6.3.15 batbinevt: Incorrect Handling of float point DPHs
Task: batbinevt
Version: 1.8 and earlier
What Builds: Swift 1.1 and earlier
Problem: Floating point DPHs were miscounted
Status: Corrected for Swift 1.2
Discussion: batbinevt reads detector plane histograms (DPHs). DPHs are commonly stored as
integer counts, but can be stored as floating point (fractional) counts. A floating point DPH can
be created by downstream processing, such as by baterebin, which reassigns fractional counts to
each energy bin.
batbinevt was reading all DPHs as integers. Floating point counts were truncated at the integer
level, resulting in (sometimes severe) undercounts.
This has been fixed for build 12.
6.3.16 batmasktaglc: light curve error bars too small
Task: batmasktaglc
Version: 2.2 and earlier
What Builds: Swift 1.1 and earlier
Problem: Light curve error bars too small
Status: Corrected for Swift 1.2
Discussion: BAT mask tagged light curves are generated on board. These raw light curves
require further processing before they are meaningful. More specifically, the raw light curves are
generated using unbalanced mask weights. The task batmasktaglc accounts for this, and generates
background-subtracted (balanced) light curves.
Versions 2.2 and earlier of the task incorrectly calculated the light curve error bars. This has
been corrected for build 12.
6.3.17 batmaskwtevt/batmaskwtimg: High-Energy Background Contamination
Task: batmaskwtevt and batmaskwtimg
Version: 1.5 and earlier
What Builds: Swift 1.1 and earlier (Build 11 and earlier)
Problem: Background contaminates spectrum at high energies
Status: Closed (Swift 1.2)
The mask weighting approach to extracting flux requirees that the weights be balanced. That
is, the sum of the weights must be zero. If they are not, then it is possible for the background to
contaminate a weighted spectrum or light curve. This would be especially apparent at high energies
where the intrinsic source flux is typically low.
Versions 1.5 of batmaskwtimg and batmaskwtevt did not have a perfectly balanced set of
weights, which led to such contamination. This was a bug, and was fixed for Swift build 12.
In BAT Build 10 (Swift 1.0) the response matrix task, batdrmgen, also had problems at high
energies. These problems were caused by the incident energy scale not extending to high enough
energies. This problem was fixed in BAT build 11 (Swift 1.1).