NuSTAR CALDB Release Version: 20191219

This is a patch release for release 20191213, in order to fix some issues with the caldb.indx20191213 file and update incorrect VERSION keywords

Release Type: GAIN and BADPIX


Summary of changes: 

BADPIX:

We have updated the list of pixels that should not be used for scientific analysis due
to their pathological response. Many of these pixels are currently non-operational, so
the inclusion of this bad pixel list should make exposure maps more accurate. The number
of bad pixels varies between detectors, but is generally less than a dozen pixels of the
1024 pixels on each detector.

GAIN

This release updates the long-term tracking of the detector. This improves the gain
accuracy after ~2017 compared with the existing CALDB gain files (v007). Since ~2016
the gain decrease of 0.2% per-year has resumed, resulting in roughly an 0.4% decrease in
the apparent energy of photons in mid-2019 compared with the current CALDB release. For
most users this change will be largely undetectable (0.004 @ 6.4 keV = ~25 eV level,
compared with the 40 PI bin resolution) except for detailed modeling of the instrumental
background lines in the 20-40 keV band.

Details of this analysis are documented at the annual meeting of the International
Astrophysical Consortium of High Energy Calibration (IACHEC, https://iachec.org) and will
be described in an upcoming paper. The latest IACHEC presentation on this topic can be
found at: https://iachec.org/wp-content/presentations/2018/Grefenstette_SessionII.pdf

Questions may be directed to the NuSTAR SOC (nustar-help@srl.caltech.edu).

Residual Issues: The long-term gain behavior of FPMA DET2 is slightly different to that
of the other 7 focal plane detectors. We make no changes to the GAIN file for this
detector in this release. Please note that for nearly all observations the source will be
located on DET0 (see the NuSTAR software user's guide for details at
https://heasarc.gsfc.nasa.gov/docs/nustar/analysis/nustar_swguide.pdf).

The long-term trends in the gain for FPMA DET2 will be addressed in a future release.
However, we note that a systematic gain offset at the 0.5% level between FPMA DET2 and
other FPM detectors may be present. Again, we expect this will only be detectable during
detailed modeling of the internal background high-energy lines. 

As always, we recommend that all users re-process their data with the new calibration
files to obtain the most accurate results.

For users who have downloaded the Level 2 (calibrated and cleaned) event data via the
HEASARC, we recommend checking the CALDBVER keyword in the FITS file header. If the
CALDBVER listed is earlier then 20191213 then we recommend reprocessing the data with the
latest calibration files.