J/MNRAS/435/1325ivo://CDS.VizieR/J/MNRAS/435/1325doi:10.26093/cds/vizier.74351325CDSMurphy S.J.Lawson W.A.Bessell M.S.2024-08-06T20:16:54Z2013-09-26T08:36:21ZCDS support team

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

cds-question@unistra.frstellar-associationspre-main-sequence-starsradial-velocitystellar-agesline-intensitiesWe present a comprehensive investigation of the {epsilon} Chamaeleontis association, one of several young moving groups spread across the southern sky. We re-assess the putative membership of {epsilon} Cha using the best available proper motion and spectroscopic measurements, including new ANU 2.3-m/Wide Field Spectrograph observations. After applying a kinematic analysis, our final membership comprises 35-41 stars from B9 to mid-M spectral types. Theoretical evolutionary models suggest {epsilon} Cha is 3-5Myr old, distinguishing it as the youngest moving group in the solar neighbourhood. 15 members show 3-22um spectral energy distributions attributable to circumstellar discs, including 11 stars which appear to be actively accreting. {epsilon} Cha's disc and accretion fractions are both consistent with a typical 3-5Myr old population. Multi-epoch spectroscopy reveals three M-type members with broad and highly variable Ha emission as well as several new spectroscopic binaries. We reject 11 stars proposed as members in the literature and suggest they may belong to the background Cha I and II clouds or other nearby young groups. Our analysis underscores the importance of a holistic and conservative approach to assigning young stars to kinematic groups, many of which have only subtly different properties and ill-defined memberships. We conclude with a brief discussion of {epsilon} Cha's connection to the young open cluster eta Cha and the Scorpius- Centaurus OB association. Contrary to earlier studies which assumed eta and {epsilon} Cha are coeval and were born in the same location, we find the groups were separated by ~30pc when eta Cha formed 4-8Myr ago in the outskirts of Sco-Cen, 1-3Myr before the majority of {epsilon} Cha members.2013MNRAS.435.1325Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/435/1325CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/357/219 : ISOCAM observations in Cha I. (Persi+, 2000)J/AJ/121/974 : JHK photometry in Cha I (Gomez+, 2001)J/AJ/124/1001 : JHKs photometry of Cha I variables (Carpenter, 2002)J/A+A/423/1029 : XMM-Newton obs, in Cha I South (Stelzer+, 2004)J/ApJ/614/267 : Chandra sources in Cha I North (Feigelson+, 2004)J/A+A/461/669 : XMM observations of Cha I dark cloud (Robrade+, 2007)J/ApJ/675/1375 : IRAC/MIPS photometry in Cha I (Luhman+, 2008)J/A+A/524/A97 : XMM observations of {eta} Cha cluster (Lopez-Santiago+, 2011)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/435/1325https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/435/1325http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/435/1325https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/435/1325https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/435/1325http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/435/1325GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/435/1325/stars (Spectroscopy, astrometry and IJHK+WISE photometry of all candidates (tables B1 and B2))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/435/1325/stars?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/435/1325/stars?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/435/1325/stars?GETtext/xml+votable180.050000true142.08791694-78.259721940.0055555555555555565/9280 6/36884 36946-36949 36956 36969 37125 37127 37137-37138 37173 41122 41128 41130 41135 41472 41474 41484 41505 41526 41528 41600-416018.157980699529898e-21 1.7798557115773645e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/435/1325?format=asciiOpticaldefaultJ/MNRAS/435/1325/membersConfirmed (table7) and provisional (table8) members of {epsilon} CharU? Heliocentric U velocitykm/sphys.veloc;pos.cartesian.xfloatnullableNameStar namemeta.id;meta.maincharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMmSimbad column added by the CDSmeta.code.membercharID[1/40]? [FLG2003] eps Cha identifier (G1)meta.idintnullableSpTMK spectral typesrc.spTypecharDistAdopted distancepcpos.distance;pos.heliocentricintf_Dist[H] Hipparcos flag (2)meta.codecharK? Magnitude of velocity difference (3)km/sphys.veloc;arith.difffloatnullableV? Heliocentric V velocitykm/sphys.veloc;pos.cartesian.yfloatnullableW? Heliocentric W velocitykm/sphys.veloc;pos.cartesian.zfloatnullableXHeliocentric X coordinatepcpos.cartesian.x;pos.heliocentricfloatYHeliocentric Y coordinatepcpos.cartesian.y;pos.galactic;pos.heliocentricfloatZHeliocentric Z coordinatepcpos.cartesian.z;pos.heliocentricfloatlogTe? Logarithm of effective temperaturelog(K)phys.temperature.effectivefloatnullablelogLb? Logarithm of bolometric luminositylog(solLum)phys.luminosityfloatnullableAge1? Age measured from Dotter isochronesMyrtime.agefloatnullableAge2? Age measured from Siess isochronesMyrtime.agefloatnullableJ/MNRAS/435/1325/starsSpectroscopy, astrometry and IJHK+WISE photometry of all candidates (tables B1 and B2)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintID[1/40]? [FLG2003] eps Cha identifier (G1)meta.idintnullableMmMembership status (from tables 7-8)meta.code.membercharNameStar namemeta.id;meta.maincharprimaryRAJ2000Right Ascension (J2000.0 degrees)degpos.eq.ra;meta.mainDEJ2000Declination (J2000.0 degrees)degpos.eq.dec;meta.mainSpTMK Spectral typesrc.spTypecharr_SpT? Reference for spectral type (1)meta.ref;pos.framecharE(B-V)? E(B-V) extinctionmagphot.color.excessfloatnullableHRV? Heliocentric radial velocitykm/sspect.dopplerVeloc;pos.heliocentricfloatnullablee_HRV? Radial velocity uncertaintykm/sstat.errorfloatnullabler_HRV? Reference for radial velocity (1)meta.ref;pos.framecharEWLi? LiI 6708{AA} equivalent width (m{AA})0.1pmspect.line.eqWidthintnullablee_EWLi? LiI EW uncertainty (m{AA})0.1pmstat.errorintnullabler_EWLi? Reference for LiI EW (1)meta.ref;pos.framecharEWHa? H-{alpha} equivalent width ({AA})0.1nmspect.line.eqWidthfloatnullableB_EWHa? Maximum H-{alpha} width if variable0.1nmspect.line.width;stat.maxfloatnullabler_EWHa? Reference for H-alpha EW (1)meta.ref;pos.framecharpmRA? Proper motion in Right Ascension pmRA*cosDEmas/yrpos.pm;pos.eq.rafloatnullablee_pmRA? Uncertainty in pmRAmas/yrstat.error;pos.pm;pos.eq.rafloatnullablepmDE? Proper motion in Declinationmas/yrpos.pm;pos.eq.decfloatnullablee_pmDE? Uncertainty in pmDEmas/yrstat.error;pos.pm;pos.eq.decfloatnullabler_pmDEReference for proper motion (1)meta.ref;pos.pm;pos.eq.deccharImag? I magnitudemagphot.mag;em.opt.Ifloatnullabler_ImagReference for I magnitude (2)meta.ref;pos.framecharJmagJ magnitudemagphot.mag;em.IR.JfloatHmagH magnitudemagphot.mag;em.IR.HfloatKmagK magnitudemagphot.mag;em.IR.Kfloatr_KmagReference for JHK magnitudes (3)meta.ref;pos.framecharW1mag? WISE W1 magnitude (3.4um) (4)magphot.mag;em.IR.3-4umfloatnullableW2mag? WISE W2 magnitude (4.6um) (4)magphot.mag;em.IR.4-8umfloatnullableW3mag? WISE W3 magnitude (12um) (4)magphot.flux.density;em.IR.8-15umfloatnullableW4mag? WISE W4 magnitude (22um) (4)magphot.flux.density;em.IR.15-30umfloatnullableSimbadSimbad column added by the CDSmeta.ref.urlcharJ/MNRAS/435/1325/refsReferencesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRefReference codemeta.notecharBibcodeBibcodemeta.bib.bibcodecharAutAuthor's namemeta.bib.authorcharComCommentsmeta.notechar