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HRASSOPTID - Hamburg/RASS Catalog: Optical Identifications

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Overview

This table is a representation of part of the Hamburg/ROSAT All-Sky Survey (RASS) Catalog (HRC) of optical identifications of X-ray sources at high-galactic latitude, namely the list of proposed and possible optical identifications. (The list of the X-ray sources themselves is given in the linked Browse table HRASSCAT). The HRC includes all X-ray sources from the ROSAT Bright Source Catalog (RASS-BSC) with galactic latitude |b| >= 30 degrees and declination Dec >= 0 degrees. In this part of the sky covering ~10,000 square degrees, the RASS-BSC contains 5341 X-ray sources. For the optical identification, the HRC authors used blue Schmidt prism and direct plates taken for the northern hemisphere Hamburg Quasar Survey (HQS) which are now available in digitized form. The limiting magnitudes are 18.5 and 20, respectively. For 82% of the selected RASS-BSC, an identification could be given. For the rest, either no counterpart was visible in the error circle, or a plausible identification was not possible. With ~42%, AGN represent the largest group of X-ray emitters, ~31% have a stellar counterpart, whereas galaxies and cluster of galaxies comprise only ~4% and ~5%, respectively. In ~3% of the RASS-BSC sources, no object was visible on the blue direct plates within 40" around the X-ray source position. The catalog has been used as a source for the selection of (nearly) complete samples of the various classes of X-ray emitters.

Catalog Bibcode

2003A&A...406..535Z

References

The Hamburg/RASS Catalogue of optical identifications.
Northern high-galactic latitude ROSAT Bright Source Catalogue X-ray sources.
    Zickgraf F.-J., Engels D., Hagen H.-J., Reimers D., Voges W.
   <Astron. Astrophys. 406, 535 (2003)>
   =2003A&A...406..535Z

Provenance

This table was produced by the HEASARC in February 2005 based on the CDS Catalog table J/A+A/406/353/optical.dat.

Description

This table is the Version 3.0 of the HRC, issued on May 6, 2003, and containing 5341 X-ray sources from the ROSAT-BSC. Version 2.0, issued on January 5, 1998 had 4665 positions (Bade et al., 1998, CDS Cat. <J/A+AS/127/145>). Version 1.1, issued on December 5, 1996, had additional entries in the X-ray rows (flags and the date of last change). Version 1.0 was issued on November 1, 1996.

The catalog can be used for scientific purposes if the paper listed in the References section is referenced. For more detailed information about the identification code and the classification scheme for objective prism spectra, the catalog user is also referred to this paper.


Acknowledgements

The ROSAT project is supported by the Ministerium fuer Bildung, Wissenschaft, Forschung und Technologie (BMBF/DARA) and by the Max-Planck-Gesellschaft (MPG).

The research on which this table is based made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. It has been funded by the Deutsche Forschungsgemeinschaft under Re 353/22-1 to 4 and by the BMBF under DARA 50 0R 96016.

The STScI Digitized Sky Surveys were produced at the Space Telescope Science Institute under U.S. Government grant NAG W-2166. The images of these surveys are based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope. The plates were processed into the present compressed digital form with the permission of these institutions. The National Geographic Society - Palomar Observatory Sky Atlas (POSS-I) was made by the California Institute of Technology with grants from the National Geographic Society.


Parameters

Name
The name of the proposed or possible optical counterpart to the X-ray source, using the naming convention recommended by the Dictionary of Nomenclature of Celestial Objects.

Xray_Name
The name of the X-Ray source, using the original ROSAT All-Sky Survey designation.

Counterpart
This parameter is a flag which is set to 'Y' to indicates that this object is the proposed Optical counterpart to the X-ray source, else it is set to 'N'. (In the published and CDS versions of the HRC, the values were '+' and ' ', respectively).

Counterpart_Num
The running number of the optical object(s) that were visible within the error circle of the X-ray source.

RA
The Right Ascension of the optical object in the selected equinox. This was given in J2000.0 coordinates and to a precision of 0.1 seconds of time in the original catalog. Two of the objects in the latter, '[ZEH2003] RX J1714.7+6442 2' and '[ZEH2003] RX J0138.5+2458 2', had blank ra and dec values: in this HEASARC table, we have placed these objects at the positions implied by their X-ray names.

Dec
The Declination of the optical object in the selected equinox. This was given in J2000.0 coordinates and to a precision of 1 arcsecond in the original catalog. Two of the objects in the latter, '[ZEH2003] RX J1714.7+6442 2' and '[ZEH2003] RX J0138.5+2458 2', had blank ra and dec values: in this HEASARC table, we have placed these objects at the positions implied by their X-ray names.

LII
The Galactic Longitude of the optical object.

BII
The Galactic Latitude of the optical object.

RA_Offset
The Right Ascension offset, in arcseconds, between the X-Ray position and the position of the optical counterpart.

Dec_Offset
The Declination offset, in arcseconds, between the X-Ray position and the position of the optical counterpart.

Total_Offset
The total offset, in arcseconds, between the X-Ray position and the position of the optical counterpart.

Limit_Bmag
This parameter is a flag which indicates a limit on the B magnitude of the optical object.

Bmag
The B magnitude of the optical object. B photometry was usually taken from the Hamburg Quasar Survey (HQS: Hagen et al. 1995, A&AS, 111, 195). The HQS B magnitudes are calibrated in the Johnson system. In the cases of bright stars, however, the HQS photometry, based on the low-resolution scans of the prism plates, did not allow the B magnitude to be measured because of the spectra being saturated. The USNO Catalog was then searched, in such cases, for the corresponding entry, and the USNO B magnitude was adopted if a matching entry was found within 5 arcseconds. This was not always the case, due to proper motion effects, and the search radius was then enlarged to 10 arcseconds. (In such cases, the value of the bmag_flag parameter has been set to 'p'). If no match was found even within 10 arcseconds, only a limit of <10.0 is given for the object's B magnitude. Occasionally, source confusion caused problems in the automatic assignment of B magnitudes from the HQS for a faint object located close to brighter objects. In order to detect these cases, the authors compared their B magnitudes with those in the USNO Catalog, and substituted USNO values if the HQS magnitude was brighter by at least 0.7 magnitudes. In such cases, the value of the bmag_flag parameter has been set to 'u'. A correction of +0.4 was applied to the USNO magnitudes in order to transform the photographic O magnitudes of the USNO to Johnson B.

Bmag_Flag
This parameter is a flag indicating a note about the B magnitude of the optical object: 'u' means that the B magnitude was taken from the USNO Catalog, 'e' means that the object was extended, 'p' means that the B magnitude was also taken from the USNO Catalog, but that, since the object has a high proper motion, the USNO - HRC matching radius which was used was 10" rather than 5", and ':' means that the B magnitude is uncertain.

Br_Color
The B-R color index of the optical object, taken from the USNO-A2.0 Catalog (CDS Catalog <I/252>).

Spectral_ID
The classification of the optical object based on the objective prism spectra, according to the following scheme:

       SUBDWARF  Hot Subdwarfs (sdO,sdB)
       W-DWARF   White Dwarfs
       STAR-BA   Balmer absorption lines, point-like image
       STAR-FG   G-Band, Ca H+K, point-like image
       STAR-K    G-Band, Ca H+K, redder continuum, point-like image
       STAR-M    Very red, TiO lines, Ca I 4226, point-like image
       CV        Cataclysmic variable, Balmer emission lines
       GALAXY    Extended image on direct plate, no emission lines, red continuum
       AGN       Emission line(s), blue continuum, weak extension on direct
                 plate allowed
       BLUE GAL  moderately blue continuum, extended image on direct plate
       QSO       Emission line(s), extremely blue continuum, no extension
                 on direct plate
       EBL-WK    Extremely blue continuum, weak point-like object
       BLUE-WK   Moderately blue continuum, weak point-like object
       RED-WK    Red continuum, weak point-like object
       UNIDENT   Classification open
       OVERLAP   Classification not possible due to overlapping spectra
       SATURATE  Classification not possible due to amplifier saturation
  

In the case of the object '[ZEH2003] RX J1116.2+4942 3', the value of this parameter in the original CDS table was 'ED-WK', and the HEASARC has changed this to 'RED-WK', assuming it was a transcription error.

Position_Note
A note when no position is given for the optical object.

Class
The HEASARC Browse object classification, based on the value of the spectral_id parameter.


Contact Person

Questions regarding the HRASSOPTID database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 23-Feb-2005