J/ApJ/461/127 J/ApJ/461/127 The Einstein Two-Sigma Catalog E C Moran D J Helfand R H Becker R L White Astrophys. J. 461 127 1996 1996ApJ...461..127M VII/152 : Einstein Medium Sensitivity Survey Catalog Moran, E.C., Helfand, D.J., Becker, R.H., White, R.L. 1996: ApJ. 461, 127. X-ray sources The X-ray sources from the observations with the Einstein Observatory (HEAO-2) with intensities of 2-sigma above the background are compiled in this catalog. This catalog covers more sky at fainter flux levels than the Einstein Medium Sensitivity Survey. Fields with diffuse emission sources were excluded. Thus data within 10 degrees of the galactic plane as well as fields within the boundaries of the Magellanic Clouds were excluded. The catalog covers 1850 sq. degrees of the sky. The generation of the Einstein Two-Sigma Catalog was described in detail by Moran et al. (1996). Read this article carefully to ensure responsible use of the Catalog. Address any questions to Ed Moran (edhed@igpp.llnl.gov). In particular it should be noted that only 28%, or about 13,000 sources in the 2-sigma catalog are real sources. The authors show that cross-correlations with other catalogs is an effective way to select sources in this catalog that are probably real.

HEAO-2

RAh RA (1950) of the source h RAm RA (1950) of the source min RAs RA (1950) of the source s DE- Sign Declination (1950) --- DEd Dec (1950) of the source deg DEm Dec (1950) of the source arcmin DEs Dec (1950) of the source arcsec S/N Signal-to-noise ratio of the source Signal-to-noise ratio of the source, based on the counts collected within a 1.25 arcmin radius circular aperture. --- IPCSEQ IPC Sequence number containing the source --- cnts125 Number of background-subtracted counts collected within a 1.25 arcmin radius circular aperture The number of background-subtracted counts contained in the source, collected within circular apertures of radii 1.25 and 2.0 arcmin. arcmin-2 cnts20 Number of background-subtracted counts collected within a 2.0 arcmin radius circular aperture arcmin-2 exp125 flatfield-weighted exposure time for the source in the 1.25 arcmin radius aperture The flatfield-weighted exposure time (sec) for the source in the 1.25 and 2.0 arcmin radius apertures. s exp20 flatfield-weighted exposure time for the source in the 2.0 arcmin radius aperture s N125 Number of "good" pixels used for count in the 1.25 arcmin radius aperture The number of ``good'' pixels used to accumulate counts for the source in the 1.25 arcmin and 2.0 arcmin radius apertures and for the background in the concentric 3-6 arcmin radius annulus. The edges of the IPC, its window support ribs, or pixel deletions resulting from the detection of brighter nearby sources can cause these numbers to be less than their maximum values of 21, 45, and 304. At least 15 of the 21 pixels in the 1.25 arcmin aperture had to be unshadowed and undeleted for a source to to be included in the Catalog. --- N20 Number of "good" pixels used for count in the 2.0 arcmin radius aperture --- Nbg Number of "good" pixels used for the background count in the concentric 3-6 arcmin radius annulus --- Paul Kuin NASA/ADC 1997Mar12 J_ApJ_461_127.xml