J/AJ/120/479ivo://CDS.VizieR/J/AJ/120/479doi:10.26093/cds/vizier.51200479CDSArdila D.Martin E.Basri G.2023-04-06T16:50:41Z2008-06-06T16:24:40ZCDS support team

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

cds-question@unistra.frpre-main-sequence-starsThe Upper Scorpius association is the OB association nearest to the Sun (145pc). Its young age (~5Myr) makes it an ideal place to search for low-mass stars and brown dwarfs, as these objects should be relatively bright. We have performed a photometric search for the low-mass members of the association, using the R, I, and Z filters. The completeness limit is I~18.5, and the saturation limit is I~13. We obtain 138 candidate members, covering nearly the entire M spectral type range. We find an excess of brown dwarf candidates over the number predicted by a Miller-Scalo initial mass function. In addition, we have performed infrared imaging and low-resolution optical spectroscopy of selected candidates. We find that the infrared observations confirm the spectral types obtained with the optical photometry. Furthermore, we find H{alpha} in emission in 20 of the 22 objects observed spectroscopically. As H{alpha} is an indicator of youth, we believe that these 20 objects may belong to the association. One of them, UScoCTIO 128, has a very strong and constant H{alpha} line (equivalent width -130{AA}), and its position in the color-magnitude diagram suggests that it is a brown dwarf with mass 0.02M_{sun}_. Confirmation of this and the other candidates will have to wait for higher resolution observations that can reveal spectroscopic mass indicators such as LiI and gravity indicators such as KI and the subordinate lines of NaI.2000AJ....120..479Ahttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/120/479CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/MNRAS/373/95 : ZYJHK survey of Upper Sco association (Lodieu+, 2006)J/MNRAS/374/372 : ZYJHK photometry in Upper Sco (Lodieu+, 2007)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/120/479https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/120/479http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/120/479https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/120/479https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/120/479http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/120/479GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AJ/120/479/table2 (RIZ candidate members in the Upper Scorpius OB association)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/120/479/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/120/479/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/120/479/table2?GETtext/xml+votable180.050000true241.7974583-17.15338890.0055555555555555565/11077 11079 6/44295 44304 44306 44315 44340 44354-44355 44360-44361 44363 44385 44387-44388 44390 44402-44403 44409 44439 44482-44483https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AJ/120/479?format=asciiOpticaldefaultJ/AJ/120/479/table2RIZ candidate members in the Upper Scorpius OB associationrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintUScoCTIOStar numbermeta.id;meta.mainintprimaryRAJ2000Right Ascension J2000pos.eq.ra;meta.mainDEJ2000Declination J2000pos.eq.dec;meta.mainImagCTIO I magnitudemagphot.mag;em.opt.Ifloate_Imagrms uncertainty on Imagmagstat.error;phot.mag;em.opt.IfloatR-ICTIO R-I colour indexmagphot.color;em.opt.R;em.opt.Ifloate_R-Irms uncertainty on R-Imagstat.error;phot.color;em.opt.RfloatSpSimbad column added by the CDSmeta.ref.urlcharSimbadSimbad column added by the CDScharJ/AJ/120/479/table3Spectroscopic observationsR-ICTIO R-I colour index (2)magphot.color;em.opt.R;em.opt.IfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintUScoCTIOStar numbermeta.id;meta.mainintl_EWHaLimit flag on EWHameta.code.errorcharEWHa? H{alpha} equivalent width (1)0.1nmspect.line.eqWidth;em.line.HalphafloatnullableSpTypeSpectral type (accuracy is half a spectral subclass)src.spTypecharAV? Reddening (accuracy is 0.5mag)magphys.absorptionfloatnullablee_R-Irms uncertainty on R-Imagstat.error;phot.color;em.opt.RfloatJmag? CIRIM J magnitudemagphot.mag;em.IR.Jfloatnullablee_Jmag? rms uncertainty on Jmagmagstat.error;phot.mag;em.IR.JfloatnullableHmag? CIRIM H magnitudemagphot.mag;em.IR.Hfloatnullablee_Hmag? rms uncertainty on Hmagmagstat.error;phot.mag;em.IR.HfloatnullableSpType2Spectral type from the I-J colour (Kirkpatrick & McCarthy, 1994AJ....107..333K)src.spTypechar