This database table consists of a preliminary source list for the Einstein Observatory's High Resolution Imager (HRI). The source list, obtained from EINLINE, the Einstein On-line Service at the Smithsonian Astrophysical Observatory (SAO), contains basic information about the sources detected with the HRI. This is a service provided by NASA HEASARC .

The HRIIMAGE database table contains information from the High Resolution Imager aboard HEAO 2, the Einstein Observatory. Einstein incorporated a high-resolution X-ray telescope and a focal plane assembly capable of positioning at its focus one of four instruments: a high-resolution imaging detector (HRI), a broader-field imaging proportional counter (HRI), a solid state spectrometer (SSS), and a Bragg crystal spectrometer (FPCS). Einstein (HEAO 2) was launched on November 13, 1978, and operated successfully until April 1981. One duplicate entry was removed from the HEASARC implementation of this catalog in June 2019. This is a service provided by NASA HEASARC .

The HRIPHOT database contains information from the High Resolution Imager aboard HEAO-2, the Einstein Observatory, in Event List Format. Einstein incorporated a high-resolution X-ray telescope and a focal plane assembly capable of positioning at its focus one of four instruments: a high- resolution imaging detector (HRI), a broader-field imaging proportional counter (IPC), a solid state spectrometer (SSS), and a Bragg crystal spectrometer (FPCS). Einstein (HEAO-2) was launched on November 13, 1978, and operated successfully until April 1981. This is a service provided by NASA HEASARC .

This database table contains primary HRI source parameters for the 202 HRI sources found in the Einstein Deep Survey. The Einstein Deep Survey (EDS) program consisted of very deep X-ray exposures in selected regions of the sky at high galactic latitude. The main purposes of the survey are to investigate the nature of the extragalactic X-ray background through direct source counts at very low flux levels and to study the nature of the very faint X-ray sources which comprise a significant fraction, if not all, of the soft X-ray background. This is a service provided by NASA HEASARC .

This database contains information on sources detected with the Einstein Observatory Image Proportional Counter (IPC), assembled for the Einstein Observatory Catalog (EOSCAT) of IPC X-ray Sources (2E) and containing over 4000 unique sources (with 6539 separate detections) which were detected with the IPC at a level of significance greater than 3.5 sigma in the broad band (0.2-3.5 keV). This database also contains the list of 277 sources which are known not to have been included in the Einstein Observatory Source Catalog (flagged by supplement = 'Y' in this database). Those which were not detected during the standard Rev1B processing were typically discovered upon visual inspection of the contour diagrams in the Catalog. Others were detected with Rev1B standard processing but left out of the Catalog because of short exposure times or other reasons listed in the "missed_code" field. 258 of these 277 additional sources have no valid signal to noise ratio (SNR) estimate (values of 0.0), while 3 others have SNR values of 3.2 and 3.3, notice. This IPC database is based on NASA Astrophysics Data System (ADS) tables that were created in 1991 and 1993 and were themselves derived from tables provided by Dr. D. E. Harris of the Center for Astrophysics at Harvard-Smithsonian. The HEASARC has a similar catalog in its database called EINSTEIN2E which comprises a more recent version of the IPC source list as archived at the NASA Astronomical Data Center (ADC) and the Center for Astronomical Data at Strasbourg (CDS). EINSTEIN2E has 868 fewer detections than the IPC catalog, notice, for reasons that the HEASARC is unsure of, but that may imply that some of the detections in IPC are not reliable. We have retained the IPC database for reasons of completeness, but caution that detections listed here which have no counterpart in the EINSTEIN2E Catalog should be treated with caution. This IPC database was recreated by the HEASARC in December 2000 to replace a previous version in which we discovered some transcription errors. It is based on NASA Astrophysics Data System (ADS) tables that were created in 1991 and 1993 and were themselves derived from tables provided by Dr. D. E. Harris of the Center for Astrophysics at Harvard-Smithsonian:

 The Einstein IPC Source List From EOSCAT (ADS Creation Date: 26-Dec-1990; ADS Last Revision Date: 04-Nov-1993), D.E. Harris, CfA The EOSCAT List of Missed IPC Sources (ADS Creation Date: 26-Oct-1990; ADS Last Revision Date: 17-Sep-1991), D.E. Harris, CfA 

This is a service provided by NASA HEASARC .

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 .

A survey of the entire Einstein IPC database (a total of 5934 sources) has been carried out in order to select objects with strong components of ultrasoft X-ray emission (i.e., emission below 0.5 keV). The selection criteria were based on ratios of counts within three broad energy bands (i.e., X-ray "colors"). A total of 516 objects have been selected, with 202 (39%) having been identified through correlations with other databases. Of the currently identified objects, 45% are active galactic nuclei, 28% are stellar objects, 6% are "normal" galaxies and galaxy clusters, and the remaining 21% are "nonstellar" Galactic objects such as cataclysmic variables, pulsars, and white dwarfs. The selection of sources for this survey was based on the analysis of counts in three broad energy bands defined as C1=0.16-0.56 keV, C2=0.56-1.08 keV, and C3= 1.08-3.5 keV. Ratios of these three bands constituted X-ray 'colors' which in turn were used to estimate the shape of the spectrum over the IPC bandpass. Based on models of X-ray spectra folded through the IPC response function, the following criteria were determined for the selection of ultrasoft sources: C1>0 and R1=C2/C1<0.36. These criteria guarantee an intrinsically soft X-ray spectrum that can be modeled by blackbody temperatures kT<50 keV, power-law spectral indices of >=2, or thermal plasma temperatures T<1 MK (million K). Details of the data analysis can be found in the Thompson et al. (1998) reference. This database was created by the HEASARC in April 1999 based on tables provided by the catalog authors to the CDS/ADC. This is a service provided by NASA HEASARC .