J/A+A/699/A262ivo://CDS.VizieR/J/A+A/699/A262doi:10.26093/cds/vizier.36990262CDSSitnova T.M.Lombardo L.Mashonkina L.I.Rizzuti F.Cescutti G.,Hansen C.J.Bonifacio P.Caffau E.Koch-Hansen A.Meynet G.,Fernandes de Melo R.2025-08-01T20:03:18Z2025-07-17T09:17:39ZCDS support team

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

cds-question@unistra.frchemically-peculiar-starschemical-abundancesastronomical-modelsWe determine the contributions of the rapid (r) and slow (s) neutron capture processes to the Ba isotope mixture, along with Ba, Eu, and Sr NLTE abundances, in a sample of very metal-poor stars. The selected stars formed before the contribution from the main s-process in low- and intermediate-mass stars became significant. Some of our sample stars are enhanced in Sr, with [Sr/Ba] reaching up to 0.7. These stars gained their high Sr abundance from a poorly understood process, sometimes referred to in the literature as a light element primary process, which may appear to be a weak s-process or a weak r-process. Our aim is to uncover the nature of this additional Sr source. The abundances derived from the resonance BaII 4554 and 4934 A lines are influenced by the adopted Ba isotope mixture. We compute Ba isotope mixtures corresponding to different r- to s-process contributions (pure r-process, 80%/20%, 50%/50% and 12%/88%, i. e. solar ratio) and determine the corresponding abundances from the BaII resonance lines in each sample star. Additionally, we determine Ba abundances from weak subordinate BaII lines, which are unaffected by the adopted Ba isotope mixture. We then compare the Ba abundances derived from the subordinate lines with those from the BaII resonance lines. We find a higher s-process contribution to Ba isotopes in stars with greater [Sr/Eu] and [Sr/Ba] overabundances, suggesting that the additional Sr synthesis was due to the early s-process occurring in massive stars. Using Sr-enhanced stars, we estimate the [Sr/Ba] ratio produced by the early s-process and obtain [Sr/Ba]_earlyS_=1.1+/-0.2. The derived value should be regarded as an upper limit, as we cannot definitively exclude the possibility of a contribution to Sr from the weak r-process, which produces Sr but not Ba. Regarding the potential synthesis of Sr and Ba in the i-process in massive stars, our results for Ba isotopes and element abundances argues that there was no detectable contribution from this process within the error bars in our sample stars. In the early Galaxy, before significant main s-process enrichment, barium and strontium were produced primarily by the main r-process and the early s-process, which occurred in rapidly rotating massive stars.2025A&A...699A.262Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/699/A262CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/699/A262https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/699/A262http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/699/A262https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/699/A262https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/699/A262http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/699/A262GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/699/A262/stars (List of studied stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/699/A262/stars?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/699/A262/stars?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/699/A262/stars?GETtext/xml+votable180.050000true11.3631667-9.54436110.0055555555555555566/51 17578 25639 26347 26457 27763 32468 34593 34595 36135 36365 44208 44575 46155 46506 46902https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/699/A262?format=asciidefaultJ/A+A/699/A262/starsList of studied starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameStar namemeta.id;meta.maincharRAJ2000Simbad right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Simbad declination (J2000)pos.eq.dec;meta.mainSNameSimbad namemeta.idcharSimbadSimbad column added by the CDSmeta.ref.urlcharJ/A+A/699/A262/table3NLTE and LTE abundances and EWs (m{AA}) of BaII lines in the starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameStar namemeta.id;meta.maincharParamParameter name (NLTE, LTE, EW) (G1)meta.id;stat.paramcharValue1BaII 4554{AA}, r/s=100/0 value for Paramstat.fit.paramfloatValue2BaII 4554{AA}, r/s=80/20 value for Paramstat.fit.paramfloatValue3BaII 4554{AA}, r/s=50/50 value for Paramstat.fit.paramfloatValue4BaII 4554{AA}, r/s=15/85 value for Paramstat.fit.paramfloatValue5BaII 4554{AA}, r/s=0/100 value for Paramstat.fit.paramfloatValue11? BaII 5853{AA} value for Paramstat.fit.paramfloatnullableValue6BaII 4934{AA}, r/s=100/0 value for Paramstat.fit.paramfloatValue7BaII 4934{AA}, r/s=80/20 value for Paramstat.fit.paramfloatValue8BaII 4934{AA}, r/s=50/50 value for Paramstat.fit.paramfloatValue9BaII 4934{AA}, r/s=12/88 value for Paramstat.fit.paramfloatValue10BaII 4934{AA}, r/s=0/100 value for Paramstat.fit.paramfloatValue12? BaII 6141{AA} value for Paramstat.fit.paramfloatnullableValue13? BaII 6496{AA} value for Paramstat.fit.paramfloatnullableJ/A+A/699/A262/table4NLTE and LTE abundances and EWs (m{AA}) from individual SrII and EuII lines in the sample starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameStar namemeta.id;meta.maincharParamParam name (NLTE, LTE, EW) (G1)meta.idcharValue1SrII 4077{AA} value for Paramstat.fit.paramfloatValue2SrII 4215{AA} value for Paramstat.fit.paramfloatValue3EuII 3819{AA} value for Paramstat.fit.paramfloatValue4EuII 4129{AA} value for Paramstat.fit.paramfloatValue5EuII 4205{AA} value for Paramstat.fit.paramfloat