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 (
Or perform, in parallel, a
single-parameter confidence limit search for a list of
parameters, with automatic refit upon discovery of a new
- 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
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
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: Apr 20, 2018