J/A+A/356/541ivo://CDS.VizieR/J/A+A/356/541doi:10.26093/cds/vizier.33560541CDSKoehler R.Kunkel M.Leinert C.Zinnecker H.2008-10-19T12:49:06Z2008-10-19T12:45:14ZCDS support team

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

cds-question@unistra.frpre-main-sequence-starsmultiple-starsx-ray-sourcesWe report the results of a search for binarity among young stars, performed in the Scorpius-Centaurus OB association on a sample of 118 X-ray selected T Tauri stars. We use speckle interferometry and direct-imaging observations to find companions in the separation range 0.13-6". After corrections to account for confusion with background stars and for the bias induced by the X-ray selection, we find a multiplicity (number of binaries or multiples divided by number of systems) of 32.6+/-6.1)%, and a number of companions per system of (35.2+/-6.3)%. This is higher by a factor of 1.59+/-0.34 compared to main-sequence stars, but slightly lower than in a sample in the Taurus-Auriga star-forming region that was selected and studied similary. In Scorpius-Centaurus, we find fewer binaries with nearly equal brightness than in Taurus-Auriga. There are significant differences between the period distributions in the two subgroups Upper Scorpius A and B: The peak of the distribution of stars in US-A is at about 10^5^ days, while that of stars in US-B is around 10^6.5^ days. We compared our results with the optical multiplicity survey of Brandner et al. (1996A&A...307..121B), whose sample contains 49 stars that were also observed by us, and find no infrared companions. The flux ratio distributions of close and wide binaries in our sample show no significant difference.2000A&A...356..541Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/356/541CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/AJ/124/1670 : Post-T Tauri Stars in Sco-Cen Association (Mamajek+, 2002)J/ApJS/82/117 : UBV and H-beta in Sco-Cen association (Slawson+, 1992)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/356/541https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/356/541http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/356/541https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/356/541https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/356/541http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/356/541GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/356/541/table1 (T Tau stars in the upper Scorpius region)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/356/541/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/356/541/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/356/541/table1?GETtext/xml+votable180.050000true231.04780194-30.516176110.0055555555555555565/10687 11029 11090 6/42719 42727 42735-42736 42739 42741-42742 42746-42747 42890 42912 42914 42920 42924 42939 44101 44111 44113-44114 44121 44125-44126 44151 44288-44289 44291 44295 44301 44305 44307-44308 44310-44312 44315-44317 44337 44364 44366-44367 44385 44388-44389 44400https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/356/541?format=asciiX-raydefaultJ/A+A/356/541/table1T Tau stars in the upper Scorpius regionRXX-ray name (1)meta.id.crosscharl_Xct[<] Limit flag on Xctmeta.code.errorcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordint[KKL2000b]Sequence numbermeta.id;meta.mainintRAJ2000Right ascension from 2MASS (J2000)degpos.eq.ra;meta.mainDEJ2000Declination from 2MASS (J2000)degpos.eq.dec;meta.mainXctCounts detected by ROSATctphot.count;em.X-rayfloatSpTypeSpectral classificationsrc.spTypecharRegion[US-AB] US-A or US-B Upper Scorpius regionmeta.notecharOTypeT Tau classification (2)meta.code.class;src.classchar2MASSName of 2MASS counterpart (1)meta.idcharROSATData from ROSAT catalogues about this sourcemeta.ref.urlchar