J/A+A/671/A21ivo://CDS.VizieR/J/A+A/671/A21doi:10.26093/cds/vizier.36710021CDSJofre P.Jorissen A.Aguilera-Gomez C.Van Eck S.Tayar J.,Pinsonneault M.Zinn J.Goriely S.Van Winckel H.2024-11-06T20:03:05Z2023-03-03T08:16:34ZCDS support team

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

cds-question@unistra.frmilky-way-galaxygiant-starsradial-velocityDetermining ages of stars for reconstructing the history of the Milky Way remains one of the most difficult tasks in astrophysics. This involves knowing when it is possible to relate the stellar mass with its age and when it is not. The young alpha-rich (YAR) stars present such a case in which we are still not sure about their ages because they are relatively massive, implying young ages, but their abundances are alpha-enhanced, which implies old ages. We report the results from new observations from a long-term radial-velocity-monitoring campaign complemented with high-resolution spectroscopy, as well as new astrometry and seismology of a sample of 41 red giants from the third version of APOKASC, which includes YAR stars. The aim is to better characterize the YAR stars in terms of binarity, mass, abundance trends, and kinematic properties. The radial velocities of HERMES, APOGEE, and Gaia were combined to determine the binary fraction among YAR stars. In combination with their mass estimate, evolutionary status, chemical composition, and kinematic properties, it allowed us to better constrain the nature of these objects. We found that stars with M<1M_{sun}_ were all single, whereas stars with M>1M_{sun}_ could be either single or binary. This is in agreement with theoretical predictions of population synthesis models. Studying their [C/N], [C/Fe], and [N/Fe], trends with mass, it became clear that many YAR stars do not follow the APOKASC stars, favoring the scenario that most of them are the product of mass transfer. Our sample further includes two likely undermassive stars, that is to say of such as low mass that they cannot have reached the red clump within the age of the Universe, unless their low mass is the signature of mass loss in previous evolutionary phases. These stars do not show signatures of currently being binaries. Both YAR and undermassive stars might show some anomalous APOGEE abundances for the elements N, Na, P, K, and Cr; although, higher-resolution optical spectroscopy might be needed to confirm these findings. Considering the significant fraction of stars that are formed in pairs and the variety of ways that makes mass transfer possible, the diversity in properties in terms of binarity, and chemistry of the YAR and undermassive stars studied here implies that most of these objects are likely not young.2023A&A...671A..21Jhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/671/A21CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)III/284 : APOGEE-2 data from DR16 (Johnsson+, 2020)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/671/A21https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/671/A21http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/671/A21https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/671/A21https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/671/A21http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/671/A21GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/671/A21/table1 (Program stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/671/A21/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/671/A21/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/671/A21/table1?GETtext/xml+votable180.050000true285.796490347.89835420.0055555555555555566/14573 14578 14581 14730 14754 14775 14779 14825 14827-14828 14914 14918 14921 14923-14924 14947 14952 14961 14965-14967 14971-14972 15109 15118-15119 15137 15140-15141 15143 15145 15149 15169 15171-151728.650015785639275e-20 3.916500758235022e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/671/A21?format=asciidefaultJ/A+A/671/A21/table1Program starsSimbadSimbad column added by the CDSmeta.ref.urlcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintVCShow the Radial Velocity curvesmeta.ref.urlcharStarStar identifiermeta.idcharKICKIC identifiermeta.id;meta.mainintAPOGEEAPOGEE identifiermeta.idcharGaiaDR3Gaia DR3 identifiermeta.idGmagGaia G magnitudemagphot.mag;em.optfloatKsmag2MASS Ks magnitudemagphot.mag;em.IR.KfloatTeffEffective temperature from APOGEE DR16, and APOKASC-3Kphys.temperature.effectiveintloggSurface gravity from APOGEE DR16, and APOKASC-3log(cm.s**-2)phys.gravityfloat[Fe/H]Metallicity from APOGEE DR16, and APOKASC-3phys.abund.Zfloat[alpha/Fe]Abundance [alpha/Fe] from APOGEE DR16, and APOKASC-3phys.abundfloat[C/N]Abundance [C/N] from APOGEE DR16, and APOKASC-3phys.abundfloatMMasssolMassphys.massfloate_MMass errorsolMassstat.errorfloatEvolEvolutionary stage of the stars (1)meta.codeint_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.main_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.mainJ/A+A/671/A21/tableb3Radial velocitiesKICKIC numbermeta.id;meta.mainintrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJDHeliocentric Julain datedtime.epochdoubleRVRadial velocitykm/sphys.veloc;pos.heliocentricfloat