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HEASARC Staff Scientist Position - Applications are now being accepted for a Staff Scientist with significant experience and interest in the technical aspects of astrophysics research, to work in the High Energy Astrophysics Science Archive Research Center (HEASARC) at NASA Goddard Space Flight Center (GSFC) in Greenbelt, MD. Refer to the AAS Job register for full details.

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XMM-NEWTON ARCHIVE

    The XMM-Newton Archive consists of the data products for the individual observations, as well as various derived catalogues, such as the XMM Serendipitous Source catalogue. Both kinds of data are accessible through on-line interfaces maintained by ESA at the XMM SOC, as well as by NASA at the XMM GOF / HEASARC.

    A separate database maintained by ESA allows you to track observation planning, execution, and data production for accepted targets.

    Observation data is subject to a proprietary period for (usually) one year after data delivery to the PI. Proprietary observation data for US based PIs (only) are available (in a PGP encoded format) at the GOF, along with all publically available observation data.

    In addition to the raw observation data the archives contain a number of pipeline data products produced for each observation. The version of the software, and associated calibration files, used for the pipeline production may not be the most recent version, though the bulk of the archive has been reprocessed through at least SAS version 7.1 (completed during the summer of 2007). Later observations generally use the most current version of the SAS at the time of the data delivery.

    XMM Science Archive (XSA)

    The SOC maintained XSA info page contains links to FAQs, manual, guides, etc., as well as the links for the various source catalogues as ASCII downloads. The XSA facility itself is a java applet wrapper around the SOC database. When you request data via the XSA you can simultaneously request that a subset of the pipeline products be reprocessed using current versions of the SAS and calibration.

    GOF Mirror Archive (Browse)

    The GOF maintained XMM-Newton observation data archive is accessed through the HEASARC Browse facility. The Browse facility also is able to access the various XMM catalogues. Reprocessing of the pipeline products must be done by the requester (See the XMM GOF Data Analysis page). Using SAS tools in SciServer Hera facility easily guarantees using the most up to date software and calibration files.

    Trend Data

    Trend data files are a one-stop access for a wide variety of satellite and operational information grouped on an XMM orbit basis and provided on a 64 second cadence. The GOF originated Trend data files can be accessed through the Trend portal.

    Optical Monitor Source Catalog (OMCat)

    OMCat is a catalogue of the serendipitous point sources found in the XMM-Newton Optical Monitor (OM). Since the OM is coaligned and records data simultaneously with the X-ray telescopes, it typically produces one or more optical or near-UV images for each pointing of the observatory. The OMCat began as an effort to process all of the OM data in a standard way to produce a master catalogue of UV/Optical sources to be compared to the XMM-Newton Serendipitous Source Catalogue, as well as a library of images for quick reference. It quickly became apparent that the standard SAS processing of the time was not producing adequate coordinate correction. As a result we executed substantial post-processing to determine the coordinate offsets compared to the USNO-B catalogue, and to correct source lists and images. The resulting source lists and images are available through the HEASARC for individual obsids (the "OM Mosiac Data" directory), while the master catalogue of sources is available through Browse (xmmomobj). Images and source catalogues for public data are also made available through the MAST archive.

    Products:
    1) Source Lists: the standard source detection routine was run on each science window, and the results concatonated. The post-processing coordinate corrections were applied.
    2) Image Mosiacs: the standard mosaics of science windows were created and the post-processing coordinate correction applied.
    3) High-Res Image Centers: the RUDI-5 format hi-res image centers were cross-correlated, shifted, and stacked, with the post-processing coordinate correction applied.

    Caveats:
    1) Since the exposure length is generally set by the X-ray requirements, the catalogue has very uneven sensitivity. Alhough there are some defaults, filter coverage is also very uneven.
    2) Since each science window of a RUDI-5 format image is taken independently, each has a different coordinate correction. For various technical reasons, OMCat was only able to apply a coordinate correction to entire images rather than individual science windows. As a result, the central window is often offset compared to the surrounding windows.
    3) There are many spurious sources due to diffraction spikes, read-out streaks, ghosts, or other optical effects. Many of these sources are flagged as optical defects, but many legitimate sources are similarly flagged, so one can not easily remove the spurious sources. Setting a S/N criterion of 3 does much to remove the spurious sources, but is not entirely successful.

    Uses:
    The OMCat's greatest strength is providing UV/Optical fluxes and counterparts to sources detected at other energies. Given the caveats above, using the catalogue to create a statistical sample of sources is unwise. Using the catalogue for finding classes of interesting sources is possible, but requires significant attention to spurious sources.

    References:
    A full description of OMCat can be found in Kuntz et al. (2008) PASP 120, 740.

    OMCat and OMCatII

    Much of the post-processing executed for OMCat has now been incorporated into SAS, as have a number of improvements suggested by the OMCat effort at GSFC. As a result, all of the public OM data is currently being reprocessed at GSFC. OMCatII will contain the same data products as OMCat, though in a slightly different format.

    Improvements:
    1.) There will be many fewer spurious sources.
    2.) The data quality flags are more meaningful.
    3.) The astrometric correction for individual sources will be better since the corrections are now done on a science window by science window basis.
    4.) Source detection is now run on both individual science windows and entire mosaics, so the source detection limit will be somewhat more sensitive.
    5.) There is some possibility of running source detection on mosaics of multiple obsids.

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