J/ApJ/448/683ivo://CDS.VizieR/J/ApJ/448/683doi:10.26093/cds/vizier.14480683CDSStern R.A.Schmitt J.H.M.M.Kahabka P.T.1997-12-09T19:54:05Z1997-12-09T20:53:59ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.fropen-star-clustersx-ray-binary-starsWe report the results of a complete X-ray survey of the Hyades cluster region using the ROSAT All-Sky Survey (RASS). Our survey covers over 900deg^2^ of the sky. Over 185 optically identified Hyades were detected down to a limiting X-ray luminosity of ~1-2x10^28^ergs/s (0.1-1.8keV); among solar-like stars, i.e., main-sequence stars of spectral type G, the RASS detection rate is ~90%. The presence of many binary systems in the cluster is a key factor influencing the X-ray luminosity function. Short-period (~ a few days or less) binaries are anomalously X-ray bright, as might be expected; however, the X-ray luminosity functions of K and possibly M binaries of all types are significantly different from their single counterparts, confirming the results of Pye et al. (1994MNRAS.266..798P) for a smaller K star sample drawn from deep ROSAT pointings. Comparison with Einstein Observatory studies of a subset of Hyades stars demonstrates a general lack of significant (> a factor of 2) long-term X-ray variability. This may be the result of the dominance of a small-scale, turbulent dynamo in the younger Hyades stars compared to the large-scale, cyclic dynamo observed in the Sun.1995ApJ...448..683Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/448/683CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toIX/11 : The ROSAT Source Catalogue (Voges+ 1995)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/448/683https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/448/683http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/448/683https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/448/683https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/448/683http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/448/683GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/448/683/table1 (Hyades survey)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/448/683/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/448/683/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/448/683/table1?GETtext/xml+votable180.050000true33.9412525.7834720.005555555555555556Cone search capability for table J/ApJ/448/683/table2 (Reid (1992, Cat. <J/MNRAS/257/257>) stars detected in X-rays)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/448/683/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/448/683/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/448/683/table2?GETtext/xml+votable180.050000true59.64916713.1051390.005555555555555556Cone search capability for table J/ApJ/448/683/table3 (Non-members in optical catalog detected in X-rays)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/448/683/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/448/683/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/448/683/table3?GETtext/xml+votable180.050000true52.6262520.0984720.005555555555555556ROSAThttps://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/448/683?format=asciiOpticaldefaultJ/ApJ/448/683/table1Hyades surveyStarStar name (1)meta.id;meta.maincharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Optical right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Optical declination (J2000)pos.eq.dec;meta.mainX-Opos? Difference in X-ray and optical positionsarcsecpos.angDistancefloatVmag? V magnitudemagphot.mag;em.opt.Vfloatr_Vmag? Reference for V magnitude (2)meta.refintB-V? B-V colour indexmagphot.color;em.opt.B;em.opt.Vfloatr_B-V? Reference for B-V index (2)meta.refintDist? Distancepcpos.distancefloatr_Dist[HS] Reference for distance (3)meta.refcharBinarityBinarity codes (4)meta.codecharM/L? Maximum likelihood ratio for X-ray source existencestat.likelihoodfloatl_LX45Limit flag on LX45meta.code.errorcharLX45X-ray luminosity based upon an assumed 45pc distanceZWphys.luminosity;em.X-rayfloate_LX45? rms uncertainty on LX45ZWstat.errorfloatl_LXdLimt flag on LXdmeta.code.errorcharLXd? X-ray luminosity using the distance from Dist columnZWphys.luminosity;em.X-rayfloate_LXd? rms uncertainty on LXdZWstat.errorfloatJ/ApJ/448/683/table2Reid (1992, Cat. <J/MNRAS/257/257>) stars detected in X-raysrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintStarStar designation (Reid number, Cat. <J/MNRAS/257/257>)meta.id;meta.maincharRAJ2000Optical right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Optical declination (J2000)pos.eq.dec;meta.mainVmag? V magnitudemagphot.mag;em.opt.VfloatB-V? B-V colour indexmagphot.color;em.opt.B;em.opt.VfloatM/L? Maximum likelihood ratio for X-ray source existencestat.likelihoodfloatPSPCPSPC countct/sphot.count;em.X-rayfloate_PSPCrms uncertainty on PSPCct/sstat.errorfloatX-Opos? Difference in X-ray and optical positionsarcsecpos.angDistancefloatNoteNotesmeta.notecharJ/ApJ/448/683/table3Non-members in optical catalog detected in X-raysrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintStarStar namemeta.id;meta.maincharRAJ2000Optical right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Optical declination (J2000)pos.eq.dec;meta.mainVmag? V magnitudemagphot.mag;em.opt.VfloatB-V? B-V colour indexmagphot.color;em.opt.B;em.opt.VfloatBinarityBinarity codes (1)meta.codecharM/L? Maximum likelihood ratio for X-ray source existencestat.likelihoodfloatPSPCPSPC countct/sphot.count;em.X-rayfloate_PSPCrms uncertainty on PSPCct/sstat.errorfloatX-Opos? Difference in X-ray and optical positionsarcsecpos.angDistancefloat