The RASS X-Ray Variable Sources Catalog contains the results of a systematic search for variability among the ROSAT All-Sky Survey (RASS) X-ray sources. Lightcurves were generated for about 30,000 X-ray point sources which were detected sufficiently high above the background. For the variability study different search algorithms were developed in order to recognize flares, periods and trends, respectively. The variable X-ray sources were optically identified with counterparts in the SIMBAD, the USNO-A2.0 and NED data bases, but a significant part of the X-ray sources remain without cataloged optical counterparts. A complete list of the 1207 X-ray variable sources that were found is presented in this table. This table was created by the HEASARC in July 2003 based on CDS table J/A+A/403/247/table7.dat. 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 .

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 .

The AllWISE program builds upon the work of the successful Wide-field Infrared Survey Explorer mission (WISE; Wright et al. 2010) by combining data from the WISE cryogenic and NEOWISE (Mainzer et al. 2011 ApJ, 731, 53) post-cryogenic survey phases to form the most comprehensive view of the full mid-infrared sky currently available. By combining the data from two complete sky coverage epochs using an advanced data processing system, AllWISE has generated new products that have enhanced photometric sensitivity and accuracy, and improved astrometric precision compared to the 2012 WISE All-Sky Data Release. Exploiting the 6 to 12 month baseline between the WISE sky coverage epochs enables AllWISE to measure source motions for the first time, and to compute improved flux variability statistics. The AllWISE Source Catalog contains accurate positions, apparent motion measurements, four-band fluxes and flux variability statistics for over 747 million objects detected on the coadded Atlas Images.

For detailed statistical analysis of the X-ray emission of hot stars, stars of spectral type O and B listed in the Yale Bright Star Catalogue were selected and searched for in the ROSAT All-Sky Survey. This database table displays a compilation of the derived X-ray data for a complete sample of bright OB stars. This is a service provided by NASA HEASARC .