J/A+A/466/917ivo://CDS.VizieR/J/A+A/466/917doi:10.26093/cds/vizier.34660917CDSCaballero J.A.2007-06-17T10:01:13Z2007-06-17T09:58:52ZCDS support team

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

cds-question@unistra.fropen-star-clustersinfrared-photometryproper-motionsThe very young sigma Orionis cluster (about 3Ma) is a cornerstone for the understanding of the formation of stars and substellar objects down to planetary masses. However, its stellar population is far to be completely known. This study has the purpose of identifying and characterising the most massive stars of sigma Orionis to complement current and future deep searches for brown dwarfs and planetary-mass objects in the cluster. I have cross-correlated the sources in the Tycho and 2MASS catalogues in a region of 30arcmin radius with centre in the O-type star sigma Ori A. In the area, I have studied the membership in the Ori OB 1b Association of the brightest stars in the optical using astrometric, X-ray and infrared and optical photometric data from public catalogues and spectroscopic data from the literature. A list of 26 young stars, four candidate young stars and 16 probable foreground stars has arised from the study. Seven young stars probably harbour discs (four are new). There is no mass-dependence of the disc frequency in the cluster. I have derived for the first time the mass spectrum in sigma Orionis from 1.1 to 24M_{sun}_ (alpha=+2.0^+0.2^_-0.1_; roughly Salpeter-like). I have also provided additional proofs on the existence of several spatially superimposed stellar populations in the direction of sigma Orionis. Finally, the cluster may be closer and older than previously considered.2007A&A...466..917Chttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/466/917CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/239 : The Hipparcos and Tycho Catalogues (ESA 1997)I/259 : The Tycho-2 Catalogue (Hog+ 2000)II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)I/297 : NOMAD Catalog (Zacharias+ 2005)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/466/917https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/466/917http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/466/917https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/466/917https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/466/917http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/466/917GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/466/917/table21 (Data of all the stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/466/917/table21?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/466/917/table21?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/466/917/table21?GETtext/xml+votable180.050000true84.68652083-2.600069440.0055555555555555566/22851 22854 228578.650015785639275e-20 1.7003137259100215e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/466/917?format=asciiInfrareddefaultJ/A+A/466/917/table21Data of all the starsHmag2MASS H magnitudemagphot.mag;em.IR.HfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameNamemeta.id;meta.maincharr_Name[a-c] note on the origin of astrometry (1)meta.ref;pos.framecharRAJ2000Right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainpmRAProper motion in right ascensionmas/yrpos.pm;pos.eq.rafloate_pmRAError in proper motion in right ascensionmas/yrstat.error;pos.pm;pos.eq.rafloatpmDEProper motion in declinationmas/yrpos.pm;pos.eq.decfloate_pmDEError in proper motion in declinationmas/yrstat.error;pos.pm;pos.eq.decfloatSpTypeMK spectral typesrc.spTypecharHRV? Heliocentric radial velocitykm/sspect.dopplerVeloc;pos.heliocentricfloatnullablee_HRV? Error in heliocentric radial velocitykm/sstat.errorfloatnullablen_Name[a-e] Individual notes (1)meta.notecharBTmagTycho-2 BT magnitudemagphot.mag;em.opt.Bfloate_BTmagError in Tycho-2 BT magnitudemagstat.error;phot.mag;em.opt.BfloatVTmagTycho-2 VT magnitudemagphot.mag;em.opt.Vfloate_VTmagError in Tycho-2 VT magnitudemagstat.error;phot.mag;em.opt.VfloatJmag2MASS J magnitudemagphot.mag;em.IR.Jfloate_JmagError in 2MASS J magnitudemagstat.error;phot.mag;em.IR.Jfloate_HmagError in 2MASS H magnitudemagstat.error;phot.mag;em.IR.HfloatKsmag2MASS Ks magnitudemagphot.mag;em.IR.Kfloate_KsmagError in 2MASS Ks magnitudemagstat.error;phot.mag;em.IR.KfloatTYCIdentification in Tycho-2 Catalogue (I/259)meta.idchar