J/A+A/627/A173ivo://CDS.VizieR/J/A+A/627/A173doi:10.26093/cds/vizier.36270173CDSValentini M.Chiappini C.Bossini D.Miglio A.Davies G.R.Mosser B.,Elsworth Y.P.Mathur S.Garcia R.A.Girardi L.Rodrigues T.S.,Steinmetz M.Vallenari A.2019-10-16T14:52:16Z2019-07-18T08:28:41ZCDS support team

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

cds-question@unistra.frchemically-peculiar-starschemical-abundanceseffective-temperatureradial-velocityVery metal-poor halo stars are the best candidates for being among the oldest objects in our Galaxy. Samples of halo stars with age determination and detailed chemical composition measurements provide key information for constraining the nature of the first stellar generations and the nucleosynthesis in the metal-poor regime. Age estimates are very uncertain and are available for only a small number of metal-poor stars. Here we present the first results of a pilot program aimed at deriving precise masses, ages and chemical abundances for metal-poor halo giants using asteroseismology, and high-resolution spectroscopy. We obtained high-resolution UVES spectra for four metal-poor RAVE stars observed by the K2 satellite. Seismic data obtained from K2 light curves helped improving spectroscopic temperatures, metallicities and individual chemical abundances. Mass and ages were derived using the code PARAM, investigating the effects of different assumptions (e.g. mass loss, [alpha/Fe]-enhancement). Orbits were computed using Gaia DR2 data. {The stars are found to be "normal" metal-poor halo stars (i.e. non C-enhanced), with an abundance pattern typical of old stars (i.e. alpha and Eu-enhanced), and with masses in the 0.80-1.0M_{sun}_ range. The inferred model-dependent stellar ages are found to range from 7.4 to 13.0Gyr, with uncertainties of ~30%-35%. We also provide revised masses and ages for metal-poor stars with Kepler seismic data from APOGEE survey and a set of M4 stars. The present work shows that the combination of asteroseismology and high-resolution spectroscopy provides precise ages in the metal-poor regime. Most of the stars analysed in the present work (covering the metallicity range of [Fe/H]~-0.8 to -2dex), are very old >9Gyr (14 out of 19 stars), and all of them are older than >5Gyr (within the 68 percentile confidence level).2019A&A...627A.173Vhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/627/A173CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/627/A173https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/627/A173http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/627/A173https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/627/A173https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/627/A173http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/627/A173GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/627/A173/table4 (Atmospheric parameters of the 4 stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/627/A173/table4?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/627/A173/table4?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/627/A173/table4?GETtext/xml+votable180.050000true178.6505411-1.56250.0055555555555555566/18451 18475 18637 25595https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/627/A173?format=asciidefaultJ/A+A/627/A173/table4Atmospheric parameters of the 4 starsRVGGAIA DR2 radial velocitykm/sphys.veloc;pos.heliocentricfloatTeffClassical effective temperatureKphys.temperature.effectiveinte_RVGrms uncertainty on GAIA DR2 radial velocitykm/sstat.errorfloate_Teffrms uncertainty on classical effective temperatureKstat.error;phys.temperature.effectiveintrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAbundDisplay the abundances of table B1meta.ref.urlcharName[S1 S2 S3 S4] Star namemeta.idcharEPICEPIC_IDmeta.id;meta.mainlongRAJ2000Right ascension (J2000) (1)degpos.eq.ra;meta.mainDEJ2000Declination (J2000) (1)degpos.eq.dec;meta.mainTeffGGAIA DR2 effective temperatureKphys.temperature.effectiveinte_TeffGrms uncertainty on GAIA DR2 effective temperatureKstat.errorintloggGGAIA DR2 surface gravity derived with parallaxlog(cm.s**-2)pos.parallaxfloate_loggGrms uncertainty on GAIA DR2 surface gravity derived with parallaxlog(cm.s**-2)stat.errorfloatloggClassical surface gravitylog(cm.s**-2)phys.gravityfloate_loggrms uncertainty on classical surface gravitylog(cm.s**-2)stat.errorfloatTeffSEffective temperature with SeismoKphys.temperature.effectiveinte_TeffSrms uncertainty on effective temperature with SeismoKstat.errorintloggSSurface gravity with Seismolog(cm.s**-2)phys.gravityfloate_loggSrms uncertainty on surface gravity with Seismolog(cm.s**-2)stat.errorfloatvmicSMicro-turbulence velocity with Seismokm/sphys.veloc.microTurbfloate_vmicSrms uncertainty on micro-turbulence velocity with Seismokm/sstat.errorfloatRVSRadial velocity with Seismokm/sphys.veloc;pos.heliocentricfloate_RVSrms uncertainty on radial velocity with Seismokm/sstat.errorfloatGaiaDR2Gaia DR2 source number (source_id)meta.idJ/A+A/627/A173/tableb1Chemical abundances derived for the metal-poor stars presented in this workrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSpeciesChemical element for which abundances are providedphys.atmol.elementcharZAtomic number of the chemical elementphys.atmol.elementfloato_AbdS1? Number of lines used for the element abundance for star S1meta.numberintnullableAbdS1? Element abundance for star S1phys.atmol.elementfloatnullablee_AbdS1? Error on element abundance for star S1stat.errorfloatnullableo_AbdS2? Number of lines used for the element abundance for star S2meta.numberintnullableAbdS2Element abundance for star S2phys.atmol.elementfloate_AbdS2Error on element abundance for star S2stat.errorfloato_AbdS3? Number of lines used for the element abundance for star S3meta.numberintnullableAbdS3Element abundance for star S3phys.atmol.elementfloate_AbdS3Error on element abundance for star S3stat.errorfloato_AbdS4? Number of lines used for the element abundance for star S4meta.numberintnullableAbdS4? Element abundance for star S4phys.atmol.elementfloatnullablee_AbdS4? Error on element abundance for star S4stat.errorfloatnullableMethodMethod used for abundance measurement (1)meta.notecharJ/A+A/627/A173/linelistLinelist adopted in the workrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambdaLine wavelength in Angstroem0.1nmem.wl;spect.linedoubleIDAtom or molecule identification numbermeta.iddoubleEPLine excitation potentialeVphys.atmol.excitation;spect.linefloatlog(gf)Line log(gf)arith.zp;spect.linefloat