XSPEC is a command-driven, interactive, X-ray spectral-fitting program. It is designed to be completely detector-independent so that it can be used for any spectrometer. To our knowledge, XSPEC has been used to analyze data from HEAO-1 A2, Einstein Observatory, EXOSAT, Ginga, ROSAT, BBXRT, ASCA, CGRO, IUE, RXTE, Chandra, and XMM-Newton. It also has been used for simulations for Swift and Astro-E2. This manual describes XSPEC v11.3, which we test build on Solaris 2.6/7/8, OSF 4.0, Mac Darwin 6.8, Linux/GNU 2.95.3 on Intel and 2.95.4 on PowerPC.
The new user is advised to read Chapter 2, which introduces spectral fitting and the XSPEC approach, Chapter 3, which gives an overview of the program commands, and Chapter 4, which contains walk-throughs of XSPEC sessions. She should then experiment with XSPEC and, if necessary, look up individual commands in Chapter 5, or descriptions of the spectral models in use, in Chapter 6. Some of the FTOOLS that can operate on XSPEC files are listed in Chapter 7. XSPEC uses the PLT plotting package, which is described briefly in Appendix A and in more detail in the ``QDP/PLT User's Guide" (Tennant, 1989). Users possessing X-ray spectra with small numbers of counts per bin are referred to Appendix B, which describes the C-statistic option. Users interested in adding their own models can read how to do so in Appendix C. The Tcl interface and XSPEC parser are described in Appendix D. Finally, Appendix E contains the recent release history.