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Description
This table contains the 132,254 AllWISE counterparts and/or Gaia matches to 106,573 X-ray sources detected in the ROSAT 2RXS survey with Galactic latitude |b| > 15 degrees. These are the brightest X-ray sources in the sky, but their position uncertainties and the sparse multi-wavelength coverage until now rendered the identification of their counterparts a demanding task with uncertain results. New all-sky multi-wavelength surveys of sufficient depth, like AllWISE and Gaia, and a new Bayesian statistics-based algorithm, NWAY, allow us, for the first time, to provide reliable counterpart associations. NWAY extends previous distance- and sky density-based association methods and, using one or more priors (e.g. colors, magnitudes), weights the probability that sources from two or more catalogs are simultaneously associated on the basis of their observable characteristics. Here, counterparts have been determined using a Wide-field Infrared Survey Explorer (WISE) color-magnitude prior. A reference sample of 4,524 XMM/Chandra and Swift X-ray sources demonstrates a reliability of 94.7 per cent for 2RXS sources. Combining the results of this work and of the matching of XMM-Newton Slew Survey, Version 2 (XMMSL2) sources also reported in this study (the results of the latter are available as the HEASARC's database table NWAYAWGXMM) with Chandra-COSMOS data, the authors propose a new separation between stars and AGN in the X-ray/WISE flux-magnitude plane, that is valid over six orders of magnitude. The authors also release the NWAY code and its user manual. NWAY was extensively tested with XMM-COSMOS data. Using two different sets of priors, the authors find an agreement of 96 per cent and 99 per cent with published Likelihood Ratio methods. Their results were achieved faster and without any follow-up visual inspection. With the advent of deep and wide area surveys in X-rays (e.g. SRG/eROSITA, Athena/WFI) and radio (ASKAP/EMU, LOFAR, APERTIF, etc.), NWAY will provide a powerful and reliable counterpart identification tool. For all the available options, see the NWAY manual at <a href="https://github.com/JohannesBuchner/nway/raw/master/doc/nway-manual.pdf">https://github.com/JohannesBuchner/nway/raw/master/doc/nway-manual.pdf</a>. This table was created by the HEASARC in February 2018 based on the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/473/4937">CDS catalog J/MNRAS/473/4937</a> file 2rxswg.dat. This is a service provided by NASA HEASARC .
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