This catalog presents X-ray data for all entries in the Third Catalogue of Nearby Stars (CNS3: Gliese and Jahreiss, 1991, ADC/CDS Cat. ) that have been detected as X-ray sources in the ROSAT All-Sky Survey (RASS). The catalog contains 1252 entries, yielding an average detection rate of 32.9 percent of the 3802 CNS3 stars. In addition to count rates, source detection parameters, X-ray hardness ratios, and X-ray fluxes, X-ray luminosities derived from Hipparcos parallaxes are also listed. For a star to have been considered by the authors to have been detected as an X-ray source in the RASS, an X-ray source with an existence likelihood of 7 or more (equivalent to a source existence probablity of 99.9 percent or more) had to lie within 90 arcseconds of its 1990 epoch CNS3 position. The choice of this cut-off radius was based on a Monte Carlo simulation of about the same number of random positions that were used as input positions. At an offset of 90 arcseconds between the optical and X-ray positions the probability that the X-ray source is attributable to the star and not to a unrelated background object is 50 percent; this probability increases very rapidly for smaller values of the offset, notice. This database was created in June 1999 based on tables provided by the ADC/CDS data centers supplemented by additional tabular material provided to the HEASARC by the author Dr. M. Huensch. This is a service provided by NASA HEASARC .

The authors have quantitatively cross-associated the 18,811 ROSAT All-Sky Survey Bright Source Catalog (RASS/BSC) X-ray sources with optical sources in the USNO A-2 catalog, calculating the probability of unique association (P_id) between each candidate within 75" of the X-ray source position, on the basis of optical magnitude and proximity. They have generated 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, they produced a total of 11,803 associations to a probability of P_id > 50%. They also 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). The authors 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. This table was created by the HEASARC in October 2009 based on electronic versions of Tables 9 (USNO counterparts for which P_id > 98%) and 10 (USNO counterparts for which 90% > P_id > 98%) of the reference paper which were obtained from the Astrophysical Journal web site. This is a service provided by NASA HEASARC .

A summary of spectroscopic identifications is presented for a complete sample of bright, soft, high galactic-latitude X-ray sources drawn from the ROSAT All-Sky Survey (RASS) which have PSPC count-rates CR>0.5cts/s, hardness ratios HR1<0, and galactic latitudes |b| > 20 degrees. Out of a total of 397 sources, 270 had previously catalogued counterparts, although most of these were not previously known as X-ray sources; of the remaining 127 sources neither X-ray nor optical properties were previously known. Of the whole sample of very soft X-ray sources 155 were also discovered by the Wide-Field-Camera on board ROSAT. Spectroscopic identifications are presented for 108 sources and other identifications for a further 18 sources; 1 source remains unidentified so far. In practically all cases a unique optical counterpart exists, facilitating identification. The largest source classes are AGN, magnetic cataclysmic variables, and hot white dwarfs This database was created by the HEASARC in April 1999 based on tables provided by the authors to CDS/ADC. This is a service provided by NASA HEASARC .

This table contains a catalog of 3405 X-ray sources from the ROSAT All Sky Survey (RASS) Bright Source Catalog which fall within the area covered by the 6dF Galaxy Survey (6dFGS). The catalog is count-rate limited at 0.05 ct s^-1 in the X-ray and covers the area of sky with Declination < 0 degrees and |b| > 10 degrees. The RASS-6dFGS sample was one of the additional target catalogs of the 6dFGS and as a result the authors obtained optical spectra for 2224 (65 per cent) RASS sources. Of these, 1715 (77%) have reliable redshifts with a median redshift of z = 0.16 (excluding the Galactic sources). For the optically bright sources (b_J <= 17.5) in the observed sample, over 90% have reliable redshifts. The catalog mainly comprises quasi-stellar objects (QSOs) and active galaxies but also includes 238 Galactic sources. Of the sources with reliable redshifts, the majority are type 1 active galactic nuclei (AGN, 69%), while 12% are type 2 AGN, 6% absorption-line galaxies and 13% are stars. The authors also identify a small number of optically faint, very low redshift, compact objects which fall outside the general trend in the b_J - z plane. The RASS-6dFGS catalog complements a number of Northern hemisphere samples, particularly the ROSAT Bright Source Catalogue-NRAO VLA Sky Survey (RBSC-NVSS) sample (Bauer et al. 2000, ApJS, 129, 547), and furthermore, in the same region of sky (-40 degrees < Declination < 0 degrees) reveals an additional 561 sources that were not identified as part of that sample. The authors detect 918 sources (27%) of the RASS-6dFGS sample in the radio using either the 1.4 GHz NVSS or the 843 MHz Sydney University Molonglo Sky Survey (SUMSS) catalogues and find that the detection rate changes with redshift. At redshifts larger than 1 virtually all of these sources have radio counterparts and with a median flux density of 1.15 Jy, they are much stronger than the median flux density of 28.6 mJy for the full sample. The authors attribute this to the fact that the X-ray flux of these objects is being boosted by a jet component, possibly Doppler boosted, that is only present in radio-loud AGN. The RASS-6dFGS sample provides a large set of homogeneous optical spectra ideal for future studies of X-ray emitting AGN. This table was created by the HEASARC in April 2010 based on an electronic version of Table 3 from the reference paper obtained from the MNRAS web site. This is a service provided by NASA HEASARC .

The 18,806 ROSAT All Sky Survey Bright Source Catalog (RASS/BSC) X-ray sources are quantitatively cross-associated with near-infrared (NIR) sources from the Two Micron All Sky Survey Point Source Catalog (2MASS/PSC). An association catalog is presented, listing the most likely counterpart for each RASS/BSC source, the probability P_id (called id_prob in the HEASARC version of this catalog) that the NIR source and X-ray source are uniquely associated, and the probability P_no-id (called no_id_prob in the HEASARC version of this catalog) that none of the 2MASS/PSC sources are associated with the X-ray source. The catalog includes 3853 high quality (P_id>0.98) X-ray-NIR matches, 2280 medium quality (0.98 >= P_id > 0.9) matches, and 4153 low quality (0.9 >= P_id > 0.5) matches. Of the high quality matches, 1418 are associations that are not listed in the SIMBAD database, and for which no high quality match with a USNO-A2 optical source was presented for the RASS/BSC source in previous work (Rutledge et al. 2000, ApJS, 131, 335). The present work offers a significant number of new associations with RASS/BSC objects that will require optical/NIR spectroscopy for classification. For example, of the 6133 P_id > 0.9 2MASS/PSC counterparts presented in the association catalog, 2411 have no classification listed in the SIMBAD database. These 2MASS/PSC sources will likely include scientifically useful examples of known source classes of X-ray emitters (white dwarfs, coronally active stars, active galactic nuclei), but they may also contain previously unknown source classes. It is determined that all coronally active stars in the RASS/BSC should have a counterpart in the 2MASS/PSC, and that the unique association of these RASS/BSC sources with their NIR counterparts thus is confusion limited. This table was created by the HEASARC in October 2009 based on an electronic version of Table 3 (the 'Association Catalog') from the paper which were obtained from the Astrophysical Journal web site. This is a service provided by NASA HEASARC .