Arnaud (photo credit Roulan Jin)

Keith Arnaud


University of Maryland
Astronomy Department

NASA Goddard
Astrophysics Science Division
X-ray Astrophysics Lab
Handbook of X-ray Astronomy

Bio CV ADS publications page ADS citations page Preprint server page Handbook of X-ray Astronomy


Refereed papers including the word xspec.
XSPEC is an interactive program used to fit models to energy spectra primarily from the X- and gamma-ray wavebands. The XSPEC manual contains tutorial examples as well as a complete command reference. We keep an up-to-date list of bugs and downloadable patches at the XSPEC issues page. New versions of XSPEC are released approximately annually with changes described in the release notes. The new models webpage contains models not available in the current XSPEC release as well as tables for table models. The FAQ answers some of the most common questions about XSPEC. Python aficionados can use XSPEC functions through the PyXspec module. Cloud versions of XSPEC are available through WebSpec, which provides limited functionality for simulations, and Hera for general use. People writing new models for XSPEC may find the internal functions guide helpful. Additional information about XSPEC can be found at the XSPEC wiki and the XSPEC Facebook group.

X-ray Astronomy Schools

In 2001 I co-founded the US X-ray astronomy school. This is intended for graduate students and postdocs as an introduction to the practical side of X-ray astronomy. The first schools comprised only lectures but when laptops became widely used we expanded to include time for attendees to work on their own data analysis tasks. These schools have been held in 2011, 2007, 2005, 2003, 2002 and 2001. An outgrowth of these schools has been the Handbook of X-ray Astronomy, written by some of the lecturers.

Also in 2001, I was one of lecturers at the first COSPAR Capacity Building Workshop. These workshops are designed to build expertise in space-based science in countries and regions which may not currently have active programs. The first workshops covered X-ray astronomy but have since expanded to planetary and Earth sciences. COSPAR X-ray astronomy workshops have been held in India in 2019, Argentina in 2017, Mexico in 2014, China in 2013, Argentina in 2011, Egypt in 2008, South Africa in 2004, India in 2003 and Brazil in 2001.


Xselect is a command-line program which wraps up many individual tools available in HEAsoft. It is designed to make X-ray astronomy data analysis simpler by obviating the need to remember how to use individual tools. A complete manual is available as well as a few general notes and specific comments for ASCA, Chandra, ROSAT, RXTE, Suzaku and XMM-Newton.


HEASP is a C++/C library with an accompanying Python module for the creation and manipulation of the files used by XSPEC. A users' guide is available in the HEAsoft distribution as $HEADAS/../heacore/help/heasp_guide.pdf or online as html or PDF. Any patches for the current release can be found at the HEASP bugs page. heasptools are a set of tools built on top of HEASP and which replace a number of older tools included in the caltools and heasarc ftools packages.
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