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HEASARC Cookbook

Analyzing Data

Addressed in this section:
  • Where can I find out about the basics of X-ray astronomy?
  • What format are HEASARC data files in?
  • What software will I need to do my data analysis?
  • How do I get started in X-ray data analysis?
  • How to I extract a spectrum and analyze it?
  • How to I extract a light curve and analyze it?
  • How to I extract an image and analyze it?
  • How do I do anything with these "event lists"?
  • How do I convert X-ray flux/energy/etc. units to those used in my field?

Where can I find out about the basics of X-ray astronomy?

An X-ray School has been set up as an annual workshop. You can peruse the viewgraphs from the 2001 X-ray School. Each year, more presentations will be added.

A more basic source of information can be found at the Imagine the Universe site which has advanced topics on

What format are HEASARC data files in?

HEASARC data are stored in FITS format. FITS is the data format most commonly used in astronomy. The fv package provides a simple way to view FITS files.

What software will I need to do my data analysis?

The HEASARC's XANADU package supports spectral, temporal and spatial analysis of high-energy data and has been developed to be quite portable. You can use this immediately on the high-level products in the HEASARC archive. The FTOOLS provide more discrete analysis tools including mission-specific analysis pipelines. These two packages were recently merged into the HEAsoft package.

Users who intend to do general analysis of X-ray data should install the entire HEAsoft suite of software; most users should download the binary distribution suitable for their particular workstation. Follow the simple installation instructions that are included with the software. Alternatively, if you know that you will only be analyzing the high level data products already in the HEASARC archive, then you may only need one or more of the the Xanadu software packages.

Instructions on using the multimission Xselect tool are available. Xselect is used to filter the raw data files and create high level spectra, light curves, and images that can then be analyzed with the Xanadu software. Mission-specific XSELECT instructions can be found for ROSAT.

How do I get started in X-ray data analysis?

For help in getting started analyzing data from specific missions, refer to the data analysis pages for each mission. These links will allow you to find user guides (usually "ABC guides" or "Getting Started" guides), calibration data, and other useful mission-specific information. For each mission there is a guide that will explain how to extract and screen the data in preparation for analysis. Some of these are listed below.

How to I extract a spectrum and analyze it?

For each mission, the screening and extraction methods are different. Please see the ABC guides listed above. Shortcuts to the relevant sections are listed below. Spectral analysis of your extracted data is generally done in the XSPEC spectral fitting package. An Overview of XSPEC and a Walkthrough of XSPEC are available as part of the User Manual.

How to I extract a light curve and analyze it?

For each mission, the screening and extraction methods are different. Please see the ABC guides listed above. Shortcuts to the relevant sections are listed below. Timing analysis of your extacted data is usually done using XRONOS. An Overview of XRONOS and a Walkthrough of XRONOS are available as part of the User Manual.

How to I extract an image and analyze it?

For each mission, the screening and extraction methods are different. Please see the ABC guides listed above. Shortcuts to the relevant sections are listed below. Image analysis of your extracted data is usually done using XIMAGE. An Overview of XIMAGE and a Getting Started primer for XIMAGE are available as part of the User Manual. A Walkthrough with examples is also available.

How do I do anything with these "event lists"?

High-energy instruments often count individual photon "events." To create the maps or time-series with which you may be more familiar, use our FTOOLS package. Many of our high-level software tools will do this for you automatically!

How do I convert X-ray flux/energy/etc. units to those used in my field?

Our W3PIMMS service can convert from the arcane units used in some X-ray papers (and a few of our catalogs) to more standard units. A general energy converter also helps translate energy units.


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Last modified: Wednesday, 13-Apr-2011 08:57:42 EDT