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Version 1.6.2-43  

ISIS Features


Using ISIS, you can:

  • Efficiently generate multi-component spectral models using the APEC/APED spectroscopy database for collisionally ionized plasmas. These spectral models may include user-defined line profiles and other forms of customization.
  • Examine ionization balance tables plus data on individual emission lines and continua.
  • (optional) Use new ISIS functionality with familiar XSPEC models. All XSPEC additive, multiplicative and convolution models are available, including table models and local models.
  • Analyze data formatted as ASCII files or FITS Type I or Type II PHA files.
  • Fit scatter data.
  • Read arbitrary FITS files and columnar ASCII tables.
  • Rebin your data interactively, with direct control over how uncertainties are propagated.
  • Factor an RSP matrix into an ARF and a normalized RMF.
  • Fit spectral models to your data either directly, or by folding models through the instrument response (parallel fitting is supported).
  • Generate fake data for Monte-Carlo analysis of model uncertainties and for proposal planning.
  • Analyze piled-up CCD spectra using the model developed by John Davis (MIT).
  • Do multi-order spectral analysis (e.g. using the Chandra/LETGS) by assigning multiple instrument responses to a single dataset.
  • Fit multiple data sets simultaneously, including an optional instrumental background component.
  • Easily combine multiple datasets, fitting a model to the summed data.
  • Define fit-parameters as arbitrary functions of other fit-parameters (including inequality constraints).
  • Impose arbitrary fit-constraints by introducing user-defined penalty functions.
  • Compute single-parameter confidence limits (conf). Or perform, in parallel, a single-parameter confidence limit search for a list of parameters, with automatic refit upon discovery of a new best-fit (see conf_loop).
  • Generate confidence contour maps in parallel; save and re-read as FITS images; plot and overplot contours.
  • Fit user-defined models coded in S-Lang, C or Fortran
  • Apply user-defined fit-statistics coded in S-Lang, C or Fortran
  • Apply user-defined fit-methods coded in S-Lang, C or Fortran
  • Apply user-defined RMFs defined in software (rather than as a FITS file)
  • Dynamically load C, C++, and FORTRAN code from external modules

Comparison with XSPEC

XSPEC users may be interested in this brief comparison of ISIS and XSPEC, which includes a table of ISIS equivalents for common XSPEC functions.

Future Releases:

Please feel free to submit comments and suggestions for new ISIS features to the ISIS mailing list.

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This page is maintained by John C. Houck.   Last updated: Feb 2, 2019