CIAO's modeling and fitting package

The CIAO 4 release features an experimental (beta) version of the new Sherpa, the CIAO modeling and fitting package. Sherpa enables the user to construct complex models from simple definitions and fit those models to data, using a variety of statistics and optimization methods.

Sherpa is designed for use in a variety of modes: as a user-interactive application and in batch mode. Sherpa is an importable module for scripting languages (Python or S-Lang) and is available as a C/C++ library for software developers. In addition, users may write their own Python and S-Lang scripts for use in Sherpa. Refer to the Should I Use Sherpa in Python or S-Lang? page for help in deciding which language to use.

Since this is the initial phase of the Sherpa redesign, not all of the functionality of the CIAO 3.4 version is implemented yet. The About the Sherpa Beta Release page outlines new features and provides a summary of missing items. Please send feedback and questions on Sherpa Beta to the Helpdesk.

Citing Sherpa in a Publication

If you are writing a paper and would like to cite Sherpa, we recommend the following paper:

\bibitem[Freeman et al.(2001)]{2001SPIE.4477...76F} Freeman, P., Doe, S., 
\& Siemiginowska, A.\ 2001, \procspie, 4477, 76

The specific version of CIAO and CALDB (if applicable) used for the analysis should be mentioned as well.

A reference for the Python interface to Sherpa is also available:

\bibitem[Doe et al.(2007)]{2007ASPC..376..543D} Doe, S., et al.\ 2007, 
Astronomical Data Analysis Software and Systems XVI, 376, 543

Further guidelines are available from the Acknowledgment of Use of Chandra Resources.