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XMM-Newton Guest Observer Facility


The XMM-Newton Extended Source Analysis Software, XMM-ESAS, is available in the SAS package. XMM-ESAS allows the user to model the quiescent particle background both spectrally and spatially for the EPIC detectors. It will produce background spectra for user-defined regions of the detectors and background images. The output files are FITS standard and can be used in spectral fitting packages (e.g., Xspec) or with FITS image display software (e.g., fv or ds9).

XMM-ESAS was developed at the NASA/GSFC XMM-Newton GOF in cooperation with the XMM-Newton SOC at ESAC and the Background Working Group. The Background Working Group consists of representatives from a number of institutions including the SOC, MPE, Leicester, Saclay, Milan, and GSFC. The focus is on extracting the greatest possible science from EPIC observations of extended sources and the diffuse background. Our goal has been to understand to the various background components experienced by the EPIC detectors, derive methods for modeling and/or removing the backgrounds, produce software to do so, and make the resulting products available to the general community. To aid astronomers, the SOC has created web pages detailing the current understanding of various background components.

A couple of papers demonstrate the utility of the XMM-ESAS analysis procedures. Snowden et al. 2004, ApJ,610,1182 Presented a serendipitous observation of solar wind charge exchange (SWCX) X-ray emission while Snowden et al. 2008, A&A, 478, 615 presented a catalog of galaxy clusters with their flux, temperature, and abundance radial profiles.

The XMM-ESAS users guide can be downloaded from the GOF at: xmm-esas-v13.pdf or viewed on-line. The document is in the process of being revised for the SAS V13 release but is not quite finished, but this partially upadted version is better than the old one as things changed significantly.

The additional CalDB files required be XMM-ESAS can be downloaded from the GOF at: esas-caldb-sasv13.tar.gz.

ESAS examples (SAS V13) of Imaging, Spectral Analysis, Mosaicking and of Mosaic Mode Observations are available.

If problems arise or if the results look odd, please contact the GSFC GOF Helpdesk at: Suggestions for improving the software or documentation are also welcome.


  • Creation of background-subtracted, exposure-corrected images of Abell 1795.
  • Creation of files required for the radial profile spectral analysis of Abell 1795.
  • Creation of mosaic images of the the observations of the nearby galaxy M101.
  • Creation of mosaic-mode observation images of the Fermi Bubble.

    Warnings and Watchouts

    NEW - 1 November 2011

  • NOTE 1: There is a somewhat obscure failure mode if the extraction region includes by chance a very small region of one of the pn quadrants. When spectra are extracted and the region of an individual quadrant is so small that no events are included that spectrum will be created but the exposure keyword will be missing. The manifests, for example, in calls to pn_back with the following error message:

    Missing EXPOSURE keyword
    missing file: pnS003-4obj.pi

    where in this case the offending quadrant was number 4 (as indicated by the spectrum name pnS003-4obj.pi). The failure can be verified by extracting a spectrum in detector coordinates using the extraction expression. The easiest fix is to deselect the affected quadrant.

    NEW - 16 May 2011

  • NOTE 1: CalDB files should be downloaded yet again to eliminate a bug in the MOS FWC data.

    NEW - 5 May 2011

  • NOTE 1: In order to run conv-region successfully SAS verbosity must be set to 0 - setenv SAS_VERBOSITY 0 - this will change with the next release
  • NOTE 2: The FWC MOS CalDB files have been recreated and should be downloaded.

    OLDER and General Notes

  • NOTE 1: Do not run multiple tasks in the same directory at the same time as this can cause conflicts leading to significant errors.
  • NOTE 2: Occasionally the backscale calculation will fail leaving the backscal keyword as 0 (zero). This will cause the calculation of the background spectrum to fail. This probably has something to do with the complication of the selection expression and we are looking into a fix. However, until a fix is found the affected CCD should be excluded.
  • NOTE 3: If a CCD is identified by mos-back as operating in an anomalous mode processing will stop. mos-spectra and mos-back should then be rerun excluding the CCD.
  • NOTE 4: The standard light-curve filtering by espfilt removes only those time intervals where the soft proton background count rate significantly fluctuates. It will not remove a relatively constant low level background. Filtering will not remove the SP background and in most cases the user will need to fit a residual component, and will occasionally need to exercise discretion on whether the observation is salvageable.
  • NOTE 5: Short exposures are problematic. Observations with clean exposures greater than ~7 ks will probably be OK. Shorter exposures should be approached with caution. Currently pn_back and mos_back do not die gracefully with a warning. The *-spec.qdp plots should be examined for reasonableness.

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    This file was last modified on Wednesday, 09-Oct-2019 14:57:43 EDT
    Curator:Michael Arida (ADNET);

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