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EXMS - EXOSAT ME Slew Catalog



This is the first online version of the EXMS catalog. It contains information on the 1210 sources detected by EXOSAT during slew manoevers between 1983 and 1986. Each detection was obtained by searching for excesses above the background level in the light curve, fitted with the expected triangular profile due to the source passing from one side of the collimator to the other. These light curves are available for inspection from the xray account at ESTEC/ESA (telnet :://

The detection time, raw 1-8 keV count rate and position (based on the centroid of the uncertainty region) are given for all 1210 entries. 80% of entries have proposed single identifications, obtained by cross-correlation of the uncertainty region against other catalogs. For these sources, the count rates are also supplied after correction for collimator efficiency, normalised to counts/sec/half, where "half" refers to one half of the ME detector array. This ensures consistency with the entries in the ME database. Coordinates of the proposed counterpart are also given, together with object type. The remaining sources consist of cases where more than one plausible candidate lay within the uncertainty region or where no candidate could be found. For these cases, only raw count rates are supplied.

Catalog Bibcode



Reynolds et al., A&A Suppl Series, 1999, 134, p. 287.


This database is a modified copy of the exms databases available from ESTEC/ESA. It was re-built by the HEASARC in July 1999.


The index number corresponding to the original IDL file (running sequentially from 0 to 1215, in chronological order of detection). Included as an id to updating the database, but of no importance to users.

The probable identification based on correlation of the detection location against various catalogs. If no id was made, the field is labelled "nonid". If multiple id's were made, the field is labelled "multiple". If a single source has different names depending on the wavelength region, preference is given to the X-ray catalog name.

The Right Ascension (1950) in degrees, from the catalog coords of the proposed identification. A value of 1.000 indicates no single identification, implying either multiple sources in the uncertainty region, or none.

The Declination (1950) in degrees, from the catalog coords of the proposed identification. A value of -1.000 indicates no single identification, implying either multiple sources in the uncertainty region, or none.

The Right Ascension of the centroid of the uncertainty region. Each region is a narrow box spanning the collimator FOV. The long side of each box is always 1.5 degrees wide, while the width of the narrow side is a function of how well the peak in the lightcurve could be fitted.

The Declination of the centroid of the uncertainty region. See notes for RA.

Galactic Longitude from RA and DEC

Galactic Latitude from RA and DEC

The detection time of the observation. This is defined as the time when the source was passing through the center of the collimator FOV, which is therefore dependent on the quality of the fit to the peak in the lightcurve. There is therefore an error associated with this detection time.

The uncertainty on the detection time, in hours, due to the uncertainty in fitting the centroid of the peak in the lightcurve.

The 1-8 keV collimator-corrected count rate in units of cts/half/sec. For multiple and unidentified sources (quality flags 1 and 0), the quoted count rates are the raw value.

The uncertainty on the collimator-corrected count rate, or the raw count rate for multiple and unidentified sources.

The 1-8 keV raw count rate, not corrected for collimator losses or normalised to counts/sec/half.

The 1-8 keV raw count rate error.

(Q) A quality flag indicating the expected reliability of the proposed identification, and associated parameters. The flag values are defined as follows:

    flag=4: most probable identification of source lies within the
      uncertainty region.
    flag=3 most probable identification lies beyond the uncertainty
      region, but would still have passed through the FOV. The
      discrepancy between uncertainty region and source position is
      most likely caused by time variability in the source, (eg for
      X-ray binaries). The count rates may be significantly affected.
    flag=2: Although the proposed identification is the brightest
      source in the uncertainty region, a second (or third) fainter
      source may contribute 25 % or less of the counts, based on
      RASSBSC fluxes.
    flag=1: Only multiple identifications proposed; no preferred
    flag=0: No identification proposed.

The uniform designation of the EXMS entry. Obtained by truncating the ra and dec of the centroid of the uncertainty region, (for 1950 original coordinates). Non-unique EXMS designations are differentiated by an additional suffix "A","B" etc, denoting the chronological order of detection.

The type of object proposed as the identification, or the catalog from which the identification is drawn. The following codes are used:

    XRB: identification from the X-ray binary catalog of van Paradijs
    RIT: identification from the Ritter catalog of CV's and LMXB's.
    VST: identification from the variable star catalog.
    SNR: source is a supernova remnant.
    VER: identification from the Veron96 catalog of AGN & QSO's.
    AGN: source is an AGN.
    CLU: source is a cluster of galaxies (usually from the Abell catalog)
    RAD: identification from the master catalog of radio sources.
    XRA: identification from the master catalog of X-ray sources.
    RAS: identification from the RASSBSC (Rosat bright sources.)
    ----: no identification proposed.

The chi2 of the fit to the collimator profile.

The likelihood statistic of the fit.

The configuration of the quadrant(s) in which the source was detected - offset, aligned or all aligned.

The collimator distance of the proposed identification. (-60 for non-identified or multiple sources). The distance is given in arc minutes. Sources close to the edge of the collimator (FWHM=45') may have substantial systematic errors in their corrected count rates, especially for extended sources. These can be selected out of any samples using the "sif" commands.

Contact Person

Questions about the contents of the EXMS database should be addressed to Questions about the EXMS database table should be addressed to the HEASARC User Hotline.
Page Author: Browse Software Development Team
Last Modified: Wednesday, 29-Jan-2020 16:34:31 EST