NuSTAR Analysis


HEASoft, the FTOOLS and XANADU software package maintained at the HEASARC, is recommended for the analysis of NuSTAR data. The current version (6.15.1) of HEASoft which was released on January 28th, 2014, contains a NuSTAR subpackage of tasks - NuSTARDAS - which, together with the existing FTOOLS and XANADU tasks, will enable users to do a complete analysis of NuSTAR datasets, with perhaps a few exceptions.

For more detailed information, see the NuSTAR data analysis software users guide, v1.5 (1.4 MB PDF file) and the NuSTAR data analysis quickstart guide, v1.0 (2.3 MB PDF file).


Known NuSTAR Analysis Issues

These will be addressed in a future release of NuSTARDAS and NuSTAR CALDB. The NuSTARDAS module that will be updated is indicated in parentheses ():

  • NuSTARDAS v1.3.1 (released as part of HEASOFT 6.15.1) is not compatible with NuSTAR CALDB version 20130509. In particular, nupipeline will fail when trying to process data with NuSTARDAS v1.3.1 and version 20130509 of the NuSTAR caldb. NuSTARDAS v1.3.1 users should either make sure they have version 20131223 of the NuSTAR caldb installed locally or that they are using remote access to access the latest NuSTAR CALDB from the HEASARC.


Previous NuSTAR Analysis Issues Which Have Been Fixed

[1] means the issue was fixed in NuSTARDAS v1.3.0 (released with HEASOFT 6.15).

[2] means that the issue was fixed in CALDB release 20131007.

[3] means that the issue was fixed in CALDB release 20131223.

[4] means the issue was fixed in NuSTARDAS v1.3.1 (released with HEASOFT 6.15.1).

  • An adjustment of the NuSTAR FPM effective areas above 50 keV was needed to correct for the residuals of the W k-edge (69.5 keV) and the Pt k-edge (78.4 keV) in CALDB version 20131007 (and earlier). Analysis of very bright objects may show smooth residual features of order 5 - 15% at energies above 50 keV. This adjustment was included in the NuSTAR CALDB patch 20131223, which was released on January 17, 2014. [3]

  • As of CALDB version 20131007, the NuSTAR clock correction file for use with the FTOOL barycorr is available within the standard HEASARC CALDB releases/patches. It is also available from the NuSTAR SOC website. [2]

  • Bad/hot pixels were only approximately accounted for in the exposure maps. There is now an improved algorithm for inclusion of bad/hot pixels in exposure maps which requires new CALDB files of instrument cumulative probability maps. (nuexpomap) [1]

  • The energy dependence of the vignetting correction to PSF was not taken account of. The corrections for the dependence of the PSF on energy are at most 5%. This correction, performed in 6 energy bands (3-4.5, 4.5-6, 6-8, 8-12, 12-20, 20-79 keV), required new CALDB PSF files. (numkarf) [1]

  • There was a processor memory issue handling temporary FITS files in the extended source case when using a small value of the input parameter 'boxsize'.This was fixed. (numkarf) [1]

  • A correction for energy-dependent PSF losses in lightcurve file generation required using new CALDB PSF files. (nulccorr) [1]

  • Adjustment of the NuSTAR FPM effective areas by +15% placed NuSTAR measured fluxes between Swift and XMM measurements based on simultaneous observations of calibration targets in 2012. [2]

  • The value of the DEADC FITS keyword affected how lightcurves are displayed. The "DEADC" FITS header keyword in the NuSTAR lightcurve files (produced by nuproducts/nupipeline) contains the average livetime fraction over the course of the observation (i.e. the livetime integrated over GTIs divided by the "real" seconds integrated over the GTIs). Some standard tools for plotting lightcurves (i.e. the "lcurve" FTOOL) read the DEADC FITS header keyword value and apply this value to the displayed lightcurve. However, the nulccorr FTOOL in NuSTARDAS v1.3.0 (and previous versions) applied a deadtime correction to each individual bin in the lightcurve. Thus using lcurve to display a NuSTAR lightcurve which has been corrected by nulccorr (as is the default for nupipeline/nuproducts) resulted in a "double counted" deadtime correction in the displayed lightcurve, and as a result over-estimated the source flux in each bin. In the meantime users can work around this by either a) setting the DEADC keyword values to 1.0 in the the NuSTAR lightcurve file before using lcurve or b) using the DEADC value to rescale the lightcurve displayed in lcurve. For example:
    % lcurve 1 out5.lc [1] rescale=0.92
    
    where out5.lc is a lightcurve file generated by nuproducts (with the parameter correctlc="yes") and 0.92 is the value of the DEADC keyword in out5.lc. [4]
  • The pilow/pihigh input parameters in nupipeline/nuproducts define the energy band over which the lightcurve is produced but as of NuSTARDAS v1.3.0 were not applied to images or spectra. The plan is to update nupipeline and nuproducts to use the pilow/pihigh keywords for image generation also so that nuproducts/nupipeline can be used to produce images as well as lightcurves in the specified energy band. For users with NuSTARDAS v1.3.0 installed (distributed as part of the heasoft-6.15 release) we recommend using the " extractor" FTOOL or XSELECT to generate images over a given energy band. [4]

  • The PIXBIN and PERC values were missing from the exposure map FITS header. The PIXBIN and PERC parameters drive the performance of nuexpomap and should have been included in the FITS header for self-documentation purposes. [4]


Notes for Specific NuSTAR Datasets

As of the date of the 3rd NuSTAR data release on February 5th, 2014, the notes for specific NuSTAR ObsID's that used to be found on this page are now captured in several parameter for those ObsIDs in the NUMASTER table. Potentially problematical issues are indicated by the parameter issue_flag in the NUMASTER table having a value set to 1. The specific nature of the issue affecting the observation will be indicated in one or more non-blank or non-zero values of the following parameters in NUMASTER: data_gap, nupsdout or solar_activity. In addition, the coordinated parameter in NUMASTER lists observatories for which coordinated observations were made with the specified NuSTAR observation. The comments parameter in NUMASTER contains a brief text synopsis of the major known issues and unusual features.


NuSTAR Calibration and Background-Subtraction Information

Documentation with information about the calibration of the NuSTAR observatory (Madsen et al. 2013, in preparation) and a detailed examination of the components of the NuSTAR background (Wik et al. 2013, in preparation) will be available shortly, at which time these references will be updated..


Most Recent NuSTAR Archive Update

The most recent release of NuSTAR data was on February 5th, 2014 and contained observations taken between 2012 July through 2013 June.