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XID: Cross-Association of ROSAT/Bright Source Catalog X-Ray Sources with USNO A-2 Optical Point Sources

Rutledge, Robert E. and Brunner, Robert J. and Prince, Thomas A. and Lonsdale, Carol (2000) XID: Cross-Association of ROSAT/Bright Source Catalog X-Ray Sources with USNO A-2 Optical Point Sources. Astrophysical Journal Supplement Series, 131 (1). pp. 335-353. ISSN 0067-0049. doi:10.1086/317363.

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We quantitatively cross-associate the 18,811 ROSAT Bright Source Catalog (RASS/BSC) X-ray sources with optical sources in the USNO A-2 catalog, calculating the probability of unique association (Pid) between each candidate within 75'' of the X-ray source position, on the basis of optical magnitude and proximity. We present catalogs of RASS/BSC sources for which P_(id) > 98%, P_(id) > 90%, and P_(id) > 50%, which contain 2705, 5492, and 11,301 unique USNO A-2 optical counterparts respectively down to the stated level of significance. Together with identifications of objects not cataloged in USNO A-2 due to their high surface brightness (M31, M32, ...) and optical pairs, we produced a total of 11,803 associations to a probability of P_(id) > 50%. We include in this catalog a list of objects in the SIMBAD database within 10'' of the USNO A-2 position, as an aid to identification and source classification. This is the first RASS/BSC counterpart catalog which provides a probability of association between each X-ray source and counterpart, quantifying the certainty of each individual association. The catalog is more useful than previous catalogs which either rely on plausibility arguments for association or do not aid in selecting a counterpart between multiple off-band sources in the field. Sources of high probability of association can be separated out, to produce high-quality lists of classes (Seyfert 1/2s, QSOs, RS CVns) desired for targeted study, or for discovering new examples of known classes (or new classes altogether) through the spectroscopic classification of securely identified but unclassified USNO A-2 counterparts. Low P_(id) associations can be used for statistical studies and follow-on investigation—for example, performing follow-up spectroscopy of the many low-mass stars to search for signatures of coronal emission, or to investigate the relationship between X-ray emission and classes of sources not previously well-studied for their X-ray emissions (such as pulsating variable stars). We find that a fraction ~65.8% of RASS/BSC sources have an identifiable optical counterpart, down to the magnitude limit of the USNO A-2 catalog which could be identified by their spatial proximity and high optical brightness.

Item Type:Article
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URLURL TypeDescription
Prince, Thomas A.0000-0002-8850-3627
Lonsdale, Carol0000-0003-0898-406X
Additional Information:© 2000. The American Astronomical Society. Received 1999 December 8; accepted 2000 April 4. The authors are grateful to the anonymous referee for careful reading of the manuscript. This paper was produced under the Digital Sky Project of the NPACI program (NSF Cooperative Agreement ACI-96-19020) and NASA grant NAG5-3239. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. This research has 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.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Subject Keywords:catalogs; X-rays: general
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Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2000-07
Issue or Number:1
Record Number:CaltechAUTHORS:20150219-091229160
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:54993
Deposited By: Deborah Miles
Deposited On:24 Feb 2015 04:31
Last Modified:28 Nov 2022 23:06

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