J/A+A/679/A110ivo://CDS.VizieR/J/A+A/679/A110doi:10.26093/cds/vizier/bc-n7/lbbaCDSGiribaldi R.E.Van Eck S.Merle T.Jorissen A.Krynski P.Planquart L.,Valentini M.Chiappini C.Van Winckel H.2026-07-01T14:01:08Z2023-11-29T09:50:55ZCDS support team

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

cds-question@unistra.frchemically-peculiar-starsgiant-starseffective-temperaturemetallicitystellar-radiiRepresentative samples of F-, G-, K-type stars located out of the Solar Neighbourhood has started to be available in spectroscopic surveys. The fraction of metal-poor ([Fe/H]<=-0.8dex) giants becomes increasingly relevant to far distances. In metal-poor stars, effective temperatures (Teff) based on LTE spectroscopy and on former colour-Teff relations of still wide use have been reported to be inaccurate. It is necessary to re-calibrate chemical abundances based on these Teff scales in the multiple available surveys to bring them to the same standard scale for their simultaneous use. For that, a complete sample of standards is required, which so far, is restricted to a few stars with quasi-direct Teff measurements. We aim at providing a legacy sample of metal-poor standards with proven accurate atmospheric parameters. We add 47 giants to the sample of metal-poor dwarfs of Giribaldi et al. (2021A&A...650A.194G, Cat. J/A+A/650/A194), thereby constituting the Titans metal-poor reference stars. Teff was derived by 3D non-LTE H{alpha} modelling, whose accuracy was tested against interferometry and InfraRed Flux Method (IRFM). Surface gravity (logg) was derived by fitting MgI b triplet lines, whose accuracy was tested against asteroseismology. Metallicity was derived using FeII lines, which was verified to be identical to the [Fe/H] derived from non-LTE spectral synthesis. Teff from 3D non-LTE H{alpha} is equivalent to interferometric and IRFM temperatures within a +/-46K uncertainty. We achieved precision of ~50K for 34 stars with spectra with the highest S/N. For log g, we achieved a total uncertainty of +/-0.15dex. For [Fe/H], we obtained a total uncertainty of +/-0.09dex. We find that the ionization equilibrium of Fe lines under LTE is not valid in metal-poor giants. LTE leads to a small but significant metallicity underestimation of ~0.1dex when derived from weak FeI lines, only provided accurate Teff and logg. This bias disappears totally under non-LTE.2023A&A...679A.110Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/679/A110CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/650/A194 : Titans metal-poor reference stars. I. (Giribaldi+, 2021)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/679/A110https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/679/A110http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/679/A110https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/679/A110https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/679/A110http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/679/A110GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/679/A110/table2 (Determined atmospheric parameters of the giant Titans)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/679/A110/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/679/A110/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/679/A110/table2?GETtext/xml+votable180.050000true7.689362257.06489690.0055555555555555566/2997 7225 8228 10476 13087 16115 16540 16698 17099 17398 17420 18707 19070 19210 19560 19923-19924 20390 21195 22205 26109-26110 26457 27871 31683 32352 33018 33470 34574 35750 35784 36414 36737 45470 45797 45818 45825 45837 46171 46512 46958 47714 48023 48501 48798 48824 49078https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/679/A110?format=asciidefaultJ/A+A/679/A110/table2Determined atmospheric parameters of the giant TitansSimbadSimbad column added by the CDSmeta.ref.urlcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameSimbad star namemeta.id;meta.maincharTeff? Effective temperatureKphys.temperature.effectiveintnullablee_Teff? Error of Effective temperatureKstat.error;phys.temperature.effectiveintnullableTeff2? Effective temperature derived by other method compatible with accurate TeffKphys.temperature.effectiveintnullablee_Teff2? Error of effective temperature derived by other method compatible with accurate TeffKstat.errorintnullableloggSurface gravitylog(cm.s**-2)phys.gravityfloate_logg? Error of surface gravitylog(cm.s**-2)stat.errorfloatnullable[FeI/H]Metallicity from neutral iron in LTEphys.abund.Zfloate_[FeI/H]Error of metallicity from neutral iron in LTEstat.error;phys.abundfloat[FeII/H]? Metallicity from ionised iron in non-LTEphys.abund.Zfloatnullablee_[FeII/H]? Error of metallicity from ionised iron in non-LTEstat.error;phys.abundfloatnullablelogL? Luminosity relative to solarlog(solLum)phys.luminosityfloatnullablee_logL? Error of Luminosity relative to solarlog(solLum)stat.errorfloatnullableRad? Radius relative to solarsolRadphys.size.radiusfloatnullablee_Rad? Error of radius relative to solarsolRadstat.errorfloatnullableA(Mg)? Magnesium abundancephys.abundfloatnullablee_A(Mg)? Error of magnesium abundancestat.errorfloatnullable_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.main