A Unified Release of the FTOOLS and XANADU Software Packages

The current version of HEAsoft is 6.26.1
(21 May 2019)

XANADU High-level, multi-mission tasks for X-ray astronomical spectral, timing, and imaging data analysis
FTOOLS General and mission-specific tools to manipulate FITS files
FITSIO Core library responsible for reading and writing FITS files (distributed with FTOOLS)
fv General FITS file browser/editor/plotter with a graphical user interface (distributed with FTOOLS)
XSTAR Tool for calculating the physical conditions and emission spectra of photoionized gases


Users may download either the source code for the software and compile the tools themselves, or download the precompiled executables for the most widely used computer platforms.

The HEAsoft Release Notes 6.26.1 give an overview of changes since HEASOFT version 6.25.

For a list of known issues in the latest release, visit the HEAsoft Known Issues page.

For help installing HEASoft on your system, please visit the appropriate link here:

Mailing List

To receive notices of HEASOFT releases, subscribe to the FTOOLS Notes mailing list by visiting



HEASOFT Developers Guide: Basic developers guide for HEASOFT is available online.

PIL Developers Guide: Developers guide for the Parameter Interface Library is available online.

Xselect Users' Guide v2.4: Available online and as pdf (256K) and tarred HTML (77K) files.

Xspec Users' Guide: Available online and as postscript (84K), tarred HTML (544K), and PDF (1.2M) files.

Ximage Users' Guide: Available online and as postscript (396K), tarred HTML (120K), and LaTeX (88K) files.

Xronos Users' Guide: Available online and as postscript (392K), tarred HTML (148K), and LaTeX (108K) files.

Previous Release Notes: 6.25, 6.24, 6.23, 6.22.1, 6.22, 6.21, 6.20, 6.19, 6.18, 6.17, 6.16, 6.15.1, 6.15, 6.14, 6.13, 6.12, 6.11.1, 6.11, 6.10, 6.9, 6.8, 6.7, 6.6.3, 6.6.2, 6.6.1, 6.6, 6.5.1, 6.5, 6.4.1, 6.4, 6.3.2, 6.3.1, 6.3, 6.2, 6.1.2, 6.1.1, 6.1, 6.0.6, 6.0.5, 6.0.4, 6.0.3, 6.0.2, 6.0, 5.3.1, 5.3, 5.2, 5.1A, 5.1, 5.0, 4.2, 4.1, 4.0, 3.6, 3.5, 3.4, 3.3, 3.2


If FTOOLS has been useful in your research, please reference this site (http://heasarc.gsfc.nasa.gov/ftools) and use the ASCL reference for HEASoft [ascl:1408.004] or the ASCL reference for the original FTOOLs paper [ascl:9912.002]:

Blackburn, J. K. 1995, in ASP Conf. Ser., Vol. 77, Astronomical Data Analysis Software and Systems IV, ed. R. A. Shaw, H. E. Payne, and J. J. E. Hayes (San Francisco: ASP), 367.

Web page maintained by: Bryan K. Irby

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