J/A+A/703/A4ivo://CDS.VizieR/J/A+A/703/A4CDSTautvaisiene G.Drazdauskas A.Mikolaitis S.Minkeviciute R.,Stonkute E.Randich S.Bragaglia A.Magrini L.Smiljanic R.,Ambrosch M.Bagdonas V.Casali G.Chorniy Y.Viscasillas Vazquez C.2026-08-28T12:18:14Z2025-10-31T07:16:01ZCDS support team

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

cds-question@unistra.frgiant-starschemical-abundancesradial-velocityeffective-temperaturevisible-astronomyspectroscopyLow- and intermediate-mass giants undergo a complex chemical evolution that has yet to be observationally probed. The influence of core helium-flash on the chemical composition of stellar atmospheres is an open question since its theoretical prediction 60 years ago. Based on high-resolution spectral observations of 44 open star clusters in the Gaia-ESO survey, our aim is to perform the first large-scale homogeneous investigation into the carbon and nitrogen photospheric content of low- and intermediate-mass giant stars in different phases of evolution. Carbon and nitrogen abundances were determined using spectral synthesis of the C2 Swan (1,0) band head at 5135{AA} and C2 Swan (0,1) band head at 5635.5{AA}, ^12^C^14^N bands in the interval 6470-6490{AA}, and the forbidden [O I] line at 6300.31{AA}. Results. We revealed differences in C/N abundance ratios between pre- and post-core-He-flash stars. The lower C/N ratios in core He-burning red clump stars are mainly due to the enhancement of nitrogen abundances. We presented calibrations of the relationship between [C/N] and stellar age for solar metallicity low- and intermediate-mass giants taking into account different evolutionary stages. The C/N abundance ratios in the investigated first-ascent giant stars are affected by the first dredge-up slightly less than predicted by the theoretical model of Lagarde et al. (2017A&A...601A..27L ). The rotation-induced extra-mixing is not as efficient as predicted by the model of Lagarde et al. ( 2012A&A...543A.108L, Cat. J/A+A/543/A108). The core helium flash may trigger additional alterations in carbon and nitrogen abundances that are not yet theoretically modelled. We found that the evolutionary stage of stars must be taken into account when using [C/N] as an age indicator.2025A&A...703A...4Thttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/703/A4CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/MNRAS/509/1664 : Membership study of 70 stars clusters (Jackson+, 2022)J/A+A/686/A42 : Improving the open cluster census. III. (Hunt+, 2024)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/703/A4https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/703/A4http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/703/A4https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/703/A4https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/703/A4http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/703/A4GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/703/A4/tablea1 (The names of the investigated OCs)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/703/A4/tablea1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/703/A4/tablea1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/703/A4/tablea1?GETtext/xml+votable180.050000true83.15320830.18466670.005555555555555556Cone search capability for table J/A+A/703/A4/tablea2 (Averaged abundances according evolutionary stages)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/703/A4/tablea2?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/703/A4/tablea2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/703/A4/tablea2?GETtext/xml+votable180.050000true83.15208330.1850.0055555555555555566/4298 14336 20562 20957 20989 21518-21519 21550 21557 21567 21719 22130 22216 22224 22239 22433 22498-22499 22887 23638 23745 24322 24330 24344-24345 28806 28822-28823 29066 30215 30635 31812 37933 37971 38441 39353 39356 41466 41613 41649 41678 42153 42177 42374 42402 42464 42496 43034 43054 43140https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/703/A4?format=asciiOpticaldefaultJ/A+A/703/A4/tablea1The names of the investigated OCsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintClusterCluster namemeta.id.parentcharIDIdentification of the star in the cluster, HHMMSSss+DDMMSSsmeta.id;meta.maincharSNRSignal-to-noise ratiostat.snrfloatTeffEffective temperatureKphys.temperature.effectiveinte_TeffUncertainty in effective temperatureKstat.error;phys.temperature.effectiveintlogglog of surface gravitylog(cm.s**-2)phys.gravityfloate_logglogg uncertaintylog(cm.s**-2)stat.errorfloatSimbadSimbad column added by the CDSmeta.ref.urlchar[Fe/H]Metallicityphys.abund.Zfloate_[Fe/H]Error of metallicitystat.error;phys.abund.FefloatVtMicroturbulent velocitykm/sphys.velocfloate_VtUncertainty in microturbulence velocitykm/sstat.errorfloat[C/H]Carbon abundancephys.abundfloate_[C/H]Uncertainty in carbon abundancestat.error;phys.abundfloat[N/H]Nitrogen abundancephys.abundfloate_[N/H]Uncertainty in nitrogen abundancestat.error;phys.abundfloat[O/H]? Oxygen abundancephys.abundfloatnullablee_[O/H]? Uncertainty in oxygen abundancestat.error;phys.abundfloatnullableC/NC/N abundance ratiophys.abundfloatEvolEvolutionary stage (1)src.classcharRVRadial velocitykm/sphys.veloc;pos.heliocentricfloate_RVUncertainty in radial velocitykm/sstat.errorfloatMHR? Membership probability according to Hunt & Reffert (2024A&A...686A..42H, Cat. J/A+A/686/A42)stat.probabilityfloatnullableMJ? Membership probability according to Jackson et al. (2022MNRAS.509.1664J, Cat. J/MNRAS/509/1664)meta.code.memberfloatnullable_RAPosition from Name (right ascension part)degpos.eq.ra;meta.main_DEPosition from Name (declination part)degpos.eq.dec;meta.mainJ/A+A/703/A4/tablea2Averaged abundances according evolutionary stagesSimbadNameSimbad column added by the CDSmeta.idcharnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintClusterCluster namemeta.id;meta.mainchar[Fe/H]Metallicityphys.abund.ZfloatMassTOTurn-off masssolMassphys.massfloatAgeAgeGyrtime.agefloatlogAgelog agelog(yr)time.agefloatRgcGalactocentric distancekpcpos.distance;pos.galactocentricfloatzMaximal distance from the galactic planekpcpos.cartesian.z;pos.galacticint[O/H]? Mean oxygen abundancephys.abundfloatnullablee_[O/H]? Scatter in the mean oxygen abundancestat.error;phys.abundfloatnullable[C/H]-BB? Mean carbon abundance in stars below the RGB luminosity bumpphys.abundfloatnullablee_[C/H]-BB? Scatter of the mean carbon abundance in stars below the RGB luminosity bumpstat.error;phys.abundfloatnullable[N/H]-BB? Mean nitrogen abundance in stars below the RGB luminosity bumpphys.abundfloatnullablee_[N/H]-BB? Scatter of the mean nitrogen abundance in stars below the RGB luminosity bumpstat.error;phys.abundfloatnullable[C/N]-BB? Mean [C/N] abundance ratio in stars below the RGB luminosity bumpphys.abundfloatnullablee_[C/N]-BB? Scatter of the mean [C/N] ratio in stars below the RGB luminosity bumpstat.error;phys.abundfloatnullableC/N-BB? Mean C/N abundance ratio in stars below the RGB luminosity bumpphys.abundfloatnullablee_C/N-BB? Scatter of the mean C/N ratio in stars below the RGB luminosity bumpstat.error;phys.abundfloatnullableNo-BB? Number of stars below RGB luminosity bumpmeta.numberintnullable[C/H]-AB? Mean carbon abundance in stars above the RGB luminosity bumpphys.abundfloatnullablee_[C/H]-AB? Scatter of the mean carbon abundance in stars above the RGB luminosity bumpstat.error;phys.abundfloatnullable[N/H]-AB? Mean nitrogen abundance in stars above the RGB luminosity bumpphys.abundfloatnullablee_[N/H]-AB? Scatter of the mean nitrogen abundance in stars above the RGB luminosity bumpstat.error;phys.abundfloatnullable[C/N]-AB? Mean [C/N] abundance ratio in stars above the RGB luminosity bumpphys.abundfloatnullablee_[C/N]-AB? Scatter of the mean [C/N] ratio in stars above the RGB luminosity bumpstat.error;phys.abundfloatnullableC/N-AB? Mean C/N abundance ratio in stars above the RGB luminosity bumpphys.abundfloatnullablee_C/N-AB? Scatter of the mean C/N ratio in stars above the RGB luminosity bumpstat.error;phys.abundfloatnullableNo-AB? Number of stars above RGB luminosity bumpmeta.numberintnullable[C/H]-clump? Mean carbon abundance in red clump starsphys.abundfloatnullablee_[C/H]-clump? Scatter of the mean carbon abundance in red clump starsstat.error;phys.abundfloatnullable[N/H]-clump? Mean nitrogen abundance in red clump starsphys.abundfloatnullablee_[N/H]-clump? Scatter of the mean nitrogen abundance in red clump starsstat.error;phys.abundfloatnullable[C/N]-clump? Mean [C/N] abundance ratio in red clump starsphys.abundfloatnullablee_[C/N]-clump? Scatter of the mean [C/N] ratio in red clump starsstat.error;phys.abundfloatnullableC/N-clump? Mean C/N abundance ratio in red clump starsphys.abundfloatnullablee_C/N-clump? Scatter of the mean C/N ratio in red clump starsstat.error;phys.abundfloatnullableNo-Clump? Number of red clump starsmeta.numberintnullable_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