The HEASARC is running nominally. If you are trying to download a lot of data, please consider using the AWS cloud copy of most HEASARC data. As an alternative to locally installing HEASoft, SciServer is an online platform which has the software installed and data available when you login.

Xspec: An X-Ray Spectral Fitting Package
Version 12.15.0 Now Available
Helpful information available includes:
- Download and installation instructions
- Xspec release notes
- Getting Help
- Xspec internal functions guide
- Xspec facebook group [external]
- External Resources
- Historical Xspec information
The latest Xspec reference is Arnaud, K.A., 1996, Astronomical Data Analysis Software and Systems V, eds. Jacoby G. and Barnes J., p17, ASP Conf. Series volume 101.
Xspec 12 was developed by:
Keith Arnaud, Ben Dorman, and Craig Gordon
HEASARC Software Development, Astrophysics Science Divsion
Code 660.1, NASA/GSFC, Greenbelt MD 20771
Please send comments, questions, and bug reports to xspechelp@athena.gsfc.nasa.gov