SIMBAD references

We cross-identified the ROSAT Bright Source Catalog (RBSC) and the NRAO VLA Sky Survey (NVSS) to construct the RBSC-NVSS sample of the brightest X-ray sources (≥0.1 counts.s^–1 ∼ 10^–12 ergs.cm^–2.s^–1 in the 0.1-2.4 keV band) that are also radio sources (S≥2.5 mJy at 1.4 GHz) in the 7.8 sr of extragalactic sky with |b|>15° and δ>-40°. The sky density of NVSS sources is low enough that they can be reliably identified with RBSC sources having rms positional uncertainties ≥10". We used the more accurate radio positions to make reliable X-ray/radio/optical identifications down to the POSS plate limits. We obtained optical spectra for many of the bright identifications lacking published redshifts. The resulting X-ray/radio sample is unique in its size (1557 objects), composition (a mixture of nearly normal galaxies, Seyfert galaxies, quasars, and clusters), and low average redshift [<z≳0.1].