J/A+A/712/A141ivo://CDS.VizieR/J/A+A/712/A141CDSGiribaldi R.E.Palla M.Magrini L.Rizzuti F.Cescutti G.Vescovi D.,Cristallo S.Belmonte M.T.Randich S.2026-08-13T07:49:08Z2026-08-13T08:48:24ZCDS support team

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

cds-question@unistra.frchemically-peculiar-starschemical-abundanceseffective-temperaturevisible-astronomyThe [Ba/Eu] abundance ratio is commonly adopted as a tracer of the relative contributions of the slow (s-) and rapid (r-) neutron-capture processes. However, at low metallicity ([Fe/H]<-2dex), barium can be produced efficiently by both processes, rendering [Ba/Eu] non-deterministic. We use the barium isotopic ratio, from the fitting of resonance Ba II line profiles affected by hyperfine splitting. This approach requires precise atomic and stellar parameters, together with advanced spectral modelling, which, so far, remained insufficiently validated. We aim to provide a robust prescription of line-profile modelling for a reliable determination of the s- and r-process fractions of barium in ordinary and peculiar stars. These observational determinations can be used to place constraints on Galactic chemical evolution models, testing yields from different astrophysical sources. We assessed the performance of one-dimensional under local thermodynamic equilibrium (1D LTE) synthesis, 1D non-LTE synthesis, and abundance corrections based on three-dimensional model atmospheres under non-LTE (3D non-LTE) to model Ba lines. Alongside barium abundances and its isotopic ratios, we determined Eu and other neutron-capture element abundances to validate the method in the TITANSmetal-poor benchmark stars. The observational results are compared with the predictions of stochastic Galactic chemical evolution models that account for the inhomogeneous mixing in the early times. We find that 1D LTE and 3D non-LTE Ba abundance determinations are equivalent, whereas the 1D non-LTE approach leads to systematic underestimations. These underestimations bias isotopic fractions towards higher r-process contributions. The inferred s- and r-process fractions demonstrate that [Ba/Eu] alone is an ambiguous tracer for ordinary stars within the -0.8<=[Ba/Eu]<=0dex range. However, we identify an observational pattern in the [Ba/Eu]-[Ba/Fe] plane that can distinguish, at a given [Ba/Fe], the dominant neutron capture process. The comparison of our set of models, both for the proto-Milky Way halo and for the Gaia-Enceladus galaxy is used to put constraints on the production of Ba at low metallicity, especially evaluating the role of rotating massive stars. The method developed here can be applied with confidence to both ordinary stars and peculiar stars enhanced in barium.2026A&A...712A.141Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/712/A141CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/650/A194 : Titans metal-poor reference stars. I. (Giribaldi+, 2021)J/A+A/673/A18 : Old Galactic stellar populations (Giribaldi+, 2023)J/A+A/679/A110 : Titans metal-poor reference stars. II. (Giribaldi+, 2023)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/712/A141https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/712/A141http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/712/A141https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/712/A141https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/712/A141http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/712/A141GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/712/A141/tablea2 (*Stellar parameters of the stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/712/A141/tablea2?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/712/A141/tablea2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/712/A141/tablea2?GETtext/xml+votable180.050000true112.671942824.08618030.0055555555555555566/373 4376 5195 6159 8205 8930 8999 12704 12793 17099 17124 17420 17509 17545 18887 19070 22205 23011 23015 23096 25385 26025 26109 26284 26289 26457 27176 27394 27857 28336 29765 30179 32352 33470 33515 33831 34574 34751 35731 35784 35913 36084 36745 38072 38216 39446 39647 39692 40391 40567 41259 42331 43445 43786 44281 44542 44653 45797 45818 46506 46512 46828 46958 47040 47147 48281 48501 48719 48736 48798 48824 49078https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/712/A141?format=asciiOpticaldefaultJ/A+A/712/A141/tablea2*Stellar parameters of the starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintStarStar namemeta.id;meta.maincharTeffEffective temperatureKphys.temperature.effectiveinte_TeffEffective temperature errorKstat.error;phys.temperature.effectiveintloggSurface gravitylog(cm.s**-2)phys.gravityfloate_loggSurface gravity errorlog(cm.s**-2)stat.errorfloat[Fe/H]NLTEMetallicity derived from 1D non-LTE analysisphys.abund.Fefloate_[Fe/H]NLTEMetallicity derived from 1D non-LTE analysis errorstat.error;phys.abund.Fefloat[Fe/H]LTE? Metallicity derived from 1D LTE analysisphys.abund.FefloatnullableVmicMicroturbulent velocitykm/sphys.velocfloatS/NSignal-to-noise ratiostat.snrintSpectSpectrograph used (1)meta.id;instrcharPopStellar population (2)meta.notecharSimbadSimbad column added by the CDSmeta.ref.urlchar_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/712/A141/tablea31D NLTE barium abundancerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintStarStar namemeta.id;meta.maincharl_A(Ba)NLTELimit flag on A(Ba)NLTEmeta.code.errorcharA(Ba)NLTE? 1D NLTE barium abundancephys.abundfloatnullable