Einstein/Ext. ivo://nasa.heasarc/exss NASA/GSFC HEASARC Oppenheimer, Helfand, Gaidos 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source The Einstein Extended Source Survey (EXSS) catalog contains a list of extended sources found in the Einstein Observatory Imaging Proportional Counter (IPC) Database. The source detection algorithm was substantially improved over that used for the Einstein Medium Sensitivity Survey (EMSS). Sources were searched for using circular apertures with variable radii of up to 6.1 arcminutes. Criteria were constructed so as to ascertain which of the detections were truly diffuse and which of the sizes best approximated each detection. Using these criteria, a catalog of 1325 extended source candidates at high galactic latitude (more than 20 degrees from the Galactic Equator) was produced. Cross-correlating this list with existing source catalogs yielded a reasonably comprehensive set of identifications for the sources in this list: over 400 were identified with known clusters of galaxies, while other objects were identified with galaxies, supernova remnants (SNR), active galactic nuclei (AGN), and stars. Whereas galaxies and SNR are often truly extended objects, AGN and stars can appear as extended ojects as a consequence of their soft X-ray spectra coupled with the broad point-spread function of the IPC at low energies. A total of 321 objects remain completely unidentified. Some of these may be heretofore uncatalogued clusters and groups of galaxies at moderate redshifts. The data used to construct this database table were obtained from the first author's Web site on 12 December 1997. This is a service provided by NASA HEASARC . 1997AJ....113.2134O https://heasarc.gsfc.nasa.gov/W3Browse/all/exss.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=exss& GET text/xml 180 99999 true 303.4072 -82.0196 0.166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=exss GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_exss&Action=More+Options&Action=Parameter+Search&ConeAdd=1 EINSTEIN 0.166666666666667 X-ray public exss Einstein Extended Source Survey name EXSS Designation meta.id;meta.main char nullable ra Right Ascension degree pos.eq.ra;meta.main double nullable dec Declination degree pos.eq.dec;meta.main double nullable count_rate_1 Aperture 1 Count Rate ct/s float nullable snr_1 Apert. 1 Signal-to-Noise Ratio float nullable count_rate_2 Aperture 2 Count Rate ct/s float nullable snr_2 Apert. 2 Signal-to-Noise Ratio float nullable "__x_ra_dec" System unit vector column double nullable "__y_ra_dec" System unit vector column double nullable "__z_ra_dec" System unit vector column double nullable "__row" System index column char nullable ra_offset_2 Apert. 2 Offset in RA (arcsec) arcsec float nullable count_rate_4 Aperture 4 Count Rate ct/s float nullable delta_dec_emss Dec Difference of EMSS Source arcsec float nullable bii Galactic Latitude degree pos.galactic.lat double nullable delta_dec_einline Dec Diff. of EINLINE Source arcsec float nullable vmag V Band Magnitude of PPM Star phot.mag;em.opt.V float nullable abell_name Designation of the Abell Cluster char nullable emss_name Designation of the EMSS Source char nullable snr_4 Apert. 4 Signal-to-Noise Ratio float nullable count_rate_3 Aperture 3 Count Rate ct/s float nullable delta_ra_abell RA Diff. of Abell Cluster arcsec float nullable ra_offset_1 Apert. 1 Offset in RA (arcsec) arcsec float nullable delta_dec_ppm Dec Difference of PPM Star arcsec float nullable snr_3 Apert. 3 Signal-to-Noise Ratio float nullable zwicky_size Approximate Size of Zwicky Cluster arcsec float nullable einline_type Type of EINLINE Source char nullable emss_type Type of the EMSS Source char nullable dec_offset_3 Apert. 3 Offset in Dec (arcsec) arcsec float nullable delta_ra_ppm RA Difference of PPM Star arcsec float nullable delta_dec_zwicky Dec Diff. of Zwicky Cluster arcsec float nullable delta_tot_einline Total Offset of EINLINE Source arcsec float nullable ppm_number PPM Star number int nullable ra_offset_3 Apert. 3 Offset in RA (arcsec) arcsec float nullable delta_ra_einline RA Diff. of EINLINE Source arcsec float nullable zwicky_name Designation of the Zwicky Cluster char nullable delta_ra_emss RA Difference of EMSS Source arcsec float nullable ra_offset_4 Apert. 4 Offset in RA (arcsec) arcsec float nullable delta_dec_abell Dec Diff. of Abell Cluster arcsec float nullable delta_ra_zwicky RA Diff. of Zwicky Cluster arcsec float nullable lii Galactic Longitude degree pos.galactic.lon double nullable emss_snr SNR of the EMSS Source float nullable dec_offset_1 Apert. 1 Offset in Dec (arcsec) arcsec float nullable dec_offset_2 Apert. 2 Offset in Dec (arcsec) arcsec float nullable dec_offset_4 Apert. 4 Offset in Dec (arcsec) arcsec float nullable