University of Birmingham

School 
of Physics and Astronomy


XMM-Newton EPIC Background Analysis



Introduction to Background Analysis Scripts

The scripts below have been developed to perform various aspects of background analysis and subtraction of XMM-Newton data, and are especially useful for the analysis of extended objects. They make extensive use of the XMM-SAS tasks, and HEASOFT's FTOOLS utilities. Though a number of the scripts may simply combine several SAS analysis steps together, it is advisable to read through a script before using it, to be clear on exactly what it does. While they have been written with generality in mind, there may be assumptions, or default values within them which are not what is required. The scripts were initially developed for use with SAS-5.2, but have been updated and configured to work with SAS-5.3. They have been developed using solaris and Linux, and have been tested, though errors may still remain, and should be reported to Andy Read  at Birmingham.
 


There are a couple of useful points to note when using the following scripts:

To download an individual script, shift-click on its name in the list below.

A zipped tarball containing all of the background analysis scripts is available here.

The scripts are written in TCSH shell, and should run on solaris or linux machines.

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Description of Individual Background Analysis Scripts

Brief descriptions of the background analysis scripts are given here. More extensive help is obtained by just typing the script name on the command line.

Before running any of these scripts, the XMM-SAS needs to be correctly configured, and all relevant SAS environment variables (e.g. SAS_ODF, SAS_CCF) need to be correctly set.
To create a background subtracted image, the relevant blank-sky background and filter-CLOSED datsets need to be skycasted. Also, the same filtering (for flares, pattern etc.) performed on the user's source dataset should be performed on the blank-sky background dataset. Once this is done, imageBGsub can be run.
To create XSPEC-compatible source and background spectra, the relevant blank-sky background dataset needs to be filtered to the same degree as the user's source dataset. A scaling value, obtained via e.g. compareoutofFOV, can then be fed into createspectra, firstly far from any source region, to create a large-radius `soft excess' spectrum. Annular source and blank-sky background spectra can then be created from the source regions via successive small-radius runs of createspectra. Finally, doublesubtraction creates a `double-background', comprising of the source background and the correctly area-scaled `soft excess' background, and associates this with a XSPEC-compatible source spectrum.

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Further pages on XMM-Newton Data Analysis at Birmingham can be found here.


Mail to Andy Read - University of Birmingham
Andy Read - Home page

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