XSPEC is a program that uses forward-fitting to analyze observed energy spectra. Parametrized theoretical models are convolved with an instrumental response and compared to the observed spectrum. Parameters are varied until a ``best-fit'' is obtained.

The current released version of XSPEC is v10.0. This is available both as source and as binaries for Linux, SunOS 4, Solaris 2, DUnix, and IRIX. The main XSPEC web page is http://legacy.gsfc.nasa.gov/docs/xanadu/xspec/index.html. Important information linked off this page includes the installation guide, the user manual, and the list of known bugs.

Bug reports and questions should be addressed to xanprob@athena.gsfc.nasa.gov

XSPEC is the world-standard software for the analysis of energy spectra in high energy astrophysics. It is in use in at least 25 countries. The word XSPEC appears in 146 papers in the ApJ since the beginning of 1997 -- this is about 3% of the papers published. WebSpec, the XSPEC web-based simulator, received about 15,000 hits in the month before the Chandra AO-1 deadline.

XSPEC is very closely linked to the FTOOLS package of tools to manipulate FITS files. FTOOLS contains many programs that users of XSPEC will find useful. We are working on better integrating XSPEC and FTOOLS to make both easier to install and run.

This poster describes some of the recent changes made to XSPEC in preparation for the next release as well as some of the longer term plans.