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Newly discovered active binaries in the RasTyc sample of stellar X-ray sources. I. Orbital and physical parameters of six new binaries
We present the first results from follow-up optical observations, bothphotometric and spectroscopic, of stellar X-ray sources, selected fromthe RasTyc sample, resulting from the cross-correlation of ROSAT All-SkySurvey (RASS) and TYCHO catalogues. In particular, we report on thediscovery of six late-type binaries, for which we obtained good radialvelocity curves and solved their orbits. We performed an automaticspectral classification of both single-lined and double-lined binarieswith codes developed by us and found two binaries composed of twomain-sequence stars and four binaries with an evolved (giant orsubgiant) component. Filled-in or pure emission Hα profilesindicative of a moderate or high level of chromospheric activity wereobserved. In nearly all the systems, we also detected a photometricmodulation ascribable to surface inhomogeneities that is correlated withthe orbital period, suggesting a synchronization between rotational andorbital periods. The position on the HR diagram of the components of thefive sources with a known parallax indicates three binaries containingonly main-sequence stars and two single-lined systems with a giantcomponent. The kinematical properties of two, or possibly four, of theobserved systems are consistent with a young disk population.
| RBSC-NVSS Sample. I. Radio and Optical Identifications of a Complete Sample of 1556 Bright X-Ray Sources
We cross-identified the ROSAT Bright Source Catalog (RBSC) and the NRAOVLA Sky Survey (NVSS) to construct the RBSC-NVSS sample of the brightestX-ray sources (>=0.1 counts s-1~10-12 ergscm-2 s-1 in the 0.1-2.4 keV band) that are alsoradio sources (S>=2.5 mJy at 1.4 GHz) in the 7.8 sr of extragalacticsky with |b|>15deg and δ>-40deg. Thesky density of NVSS sources is low enough that they can be reliablyidentified with RBSC sources having rms positional uncertainties>=10". We used the more accurate radio positions to make reliableX-ray/radio/optical identifications down to the POSS plate limits. Weobtained optical spectra for many of the bright identifications lackingpublished redshifts. The resulting X-ray/radio sample is unique in itssize (1557 objects), composition (a mixture of nearly normal galaxies,Seyfert galaxies, quasars, and clusters), and low average redshift[~0.1].
| The FIRST Unbiased Survey for Radio Stars
Comparison of the VLA FIRST survey with various catalogs of bright starsallows an examination of the prevalence of stellar radio emissionindependent of optical selection criteria. This FIRST unbiased surveyfor radio stars covers nearly 5000 deg^2 of the northern sky to a fluxdensity limit of 0.7 mJy at 20 cm. Using astrometric catalogs thatinclude proper-motion information, we have detected 26 stellar radiosources, doubling the number of such objects previously known in thisregion of high-latitude sky. We also show that, in the absence of goodproper motions, even the 1" precision of the FIRST positions isinsufficient to avoid crippling chance coincidence rates. We calculatethe fraction of radio detections as a function of stellar magnitude andshow that, when proper motions from the Guide Star Catalog II becomeavailable, the number of stellar radio source detections should increasefourfold.
| The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| Radial Velocities, Spectral Types, and Luminosity Classes of 820 Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1950ApJ...112...48M&db_key=AST
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