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The XMM-Newton General Observer Facility

Data Analysis

The GOF maintains several manuals and threads to assist in data analysis. Links to these and to potentially useful software packages are below. The software is also available on SciServer, the joint program run by NASA and JHU to facilitate data reduction in the cloud; users who do not wish to install SAS and its calibration files are encouraged to investigate SciServer. A short introduction demonstrating how to get started with SAS in SciServer can be found here.

Science Analysis System (SAS) and Extended Science Analysis System (ESAS)
SAS with Python Wrappers and Perl Scripts
Other Software You Might Find Useful
Documentation
XMM-Newton Source Naming Convention
Other Publication Guidelines



Science Analysis System (SAS) and Extended Science Analysis System (ESAS)

The Science Analysis System (SAS) provides the basic reduction tools of XMM-Newton data. It contains tasks that rerun the pipeline, apply the most recent calibrations, and allow users to filter their data. It also provides tasks for source detection, spectrum extraction, and light curve production, among many (many!) other things. It is maintained jointly by the Science Operations Center (SOC) and the GOF, with new versions released on a roughly yearly cadence. SAS can be downloaded through links at the SOC's general data analysis portal.

The Extended Science Analysis System (ESAS) provides tasks that were designed for the analysis of extended sources in the EPIC cameras (pn, MOS1, and MOS2). While initially developed by the GOF, it has now been fully integrated into the SAS, so users who want to use ESAS should install SAS.

The SAS installation file can be downloaded either from the SOC or the GOF's US mirror site. You should refer to both the detailed installation instructions, and the list of required helper applications that also must be installed.

If you aren't sure which version of the SAS you need, a handy conversion table is available.

You will also need to install the current set of calibration files.



SAS with Python Wrappers and Perl Scripts

Python wrappers and Jupyter Notebooks that demonstrate basic XMM data reduction are available at Github and on SciServer.

There are also Perl scripts that streamline the basic data reduction process for the EPIC and RGS cameras available for download. A short guides detailing their use is available following these links. In addition to simplifying data reduction, they minimize user interaction. Knowledge of SAS, while recommended, is not required.



Other Software You Might Find Useful

Gnupg (GPG) is for archive file decryption. In order to decrypt proprietary XMM-Newton data, pgp or gpg with IDEA support is needed. If you don't already have this on your system the GOF has made some static binaries available that will work with our decrypt script.

SAS does not contain tasks that allow users to perform high level scientific analysis such as spectral fitting or temporal analysis. However, the SAS product files are designed to OGIP standards, so any high-level analysis package for use in high energy astrophysics is capable of processing XMM-Newton data. Some commonly-used ones are below.

  • Xspec -- This is the HEASoft FTool subpackage for fitting spectra to models. It can accomodate X-ray and optical data (for joint fitting of EPIC and OM data sets, for instance).
  • Xronos -- This is the HEASoft FTool subpackage for analysis of timing data. It can, for instance, make a power spectrum and find the periodicity of a light curve.
  • Ximage -- This is the HEASoft FTool subpackage for analysis of images.
  • Sherpa -- This is CXC's package for analyzing X-ray data. It was developed for Chandra data, but it is compatible with XMM data. It can fit both spectra and images.
  • SPEX -- This is a spectrum fitting package produced by the Netherlands Institute for Space Research (SRON).
  • ISIS -- This is a spectrum fitting package designed for high resolution X-ray spectra. It combines all the models available in XSpec with the programmability of S-Lang.



Documentation

The GOF maintains many guides to using SAS/ESAS, as well as introductions to performing higher level analyses in some of the software packages mentioned above. These were developed with users of all levels of familiarity with SAS and X-ray data reduction in mind, from novices to experts. In addition to these, we also provide links to the observatory handbook and data guides.

  • The XMM-Newton Users Handbook can be found online at the GSFC or the SOC. G'zipped PostScript (8.8 Mbyte compressed, 98 Mbyte uncompressed) and PDF (9.4 Mbyte) versions are available.
  • The SAS Users Guide can be found online at the GSFC or the SOC. G'zipped PostScript (18 Mb) and PDF (8 Mb) versions are available.
  • Online documentation for SAS tasks (listing all the task parameters and parameter values, describing the algorithm used, and warnings and errors that a user might encounter, etc.) can be found at the GSFC or the SOC.
  • The Absolute Beginners Guide to XMM v1 was written by the GOF for scientists and students who are completely new to X-ray data analysis in general and XMM-Newton data analysis in particular, and includes a walk-through of how to get data from the archive.
  • The XMM-Newton ABC Guide for XMM data analysis, prepared by the GOF, is a companion document to SAS. It provides simple analysis walk throughs and practical information. It is geared toward people who may be generally familiar with X-ray data, but need a refresher.
  • The ESAS Cookbook is a manual made by the GOF for ESAS users. It goes into some depth about the sources of background in the EPIC cameras and in the X-ray sky and provides several examples.
  • The XMM-Newton ABC Guide Streamlined is a modified version of the ABC Guide, simplifying it and making it easier for users who are more familiar with XMM data to find what they are looking for.
  • The Data Simulation and Analysis Threads demonstrate high-level analysis and simulation of XMM data with commonly-used software packages like XSpec, Sherpa, and SIXTE.


XMM-Newton Source Naming Convention

The XMM-Newton Observatory catalogs tens of X-ray sources and additional Optical/UV targets for each and every observation. When referring to sources in XMM observations it is appropriate to use their catalog designation. For X-ray sources that have no designation that need to be referred to in a paper, you should use the naming convention XMMU JHHMMSS.s+/-DDMMSS,

e.g. source position: RA 03 10 15.1, Dec -76 51 31.2 (J2000) recommended acronym: XMMU J031015.1-765131
source position: RA 17 23 48.7, Dec +82 17 33.8 (J2000) recommended acronym: XMMU J172348.7+821733.

Note that position designations are truncated and not rounded.

The naming convention for uncatalogued optical/UV sources detected only with the Optical Monitor is still under discussion. For now, sources should be designated using the form XAU JHHMMSS.s+/-DDMMSS.

(See also the SOC source naming page.)



Other Publication Guidelines

When publishing a paper using XMM-Newton data please include the following text, preferably as a footnote to the title:

"Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA"

Each publication using XMM-Newton data should include the Target Name, the Date of the Observation and the ObsId to ensure that the data can be uniquely identified.

(From the SOC Publication Guidelines page.)

If you have any questions concerning XMM-Newton send email to xmmhelp@athena.gsfc.nasa.gov