Barium lines in high-quality spectra of two metal-poor giants in the Galactic halo

• Verfasst von: Cescutti, Gabriele [VerfasserIn]
• Verfasst von: Morossi, C. [VerfasserIn]
• Verfasst von: Franchini, M. [VerfasserIn]
• Verfasst von: Marcantonio, P. Di [VerfasserIn]
• Verfasst von: Chiappini, C. [VerfasserIn]
• Verfasst von: Steffen, M. [VerfasserIn]
• Verfasst von: Valentini, M. [VerfasserIn]
• Verfasst von: François, P. [VerfasserIn]
• Verfasst von: Christlieb, Norbert [VerfasserIn]
• Verfasst von: Cortés, C. [VerfasserIn]
• Verfasst von: Kobayashi, C. [VerfasserIn]
• Verfasst von: Depagne, E. [VerfasserIn]
• Titel: Barium lines in high-quality spectra of two metal-poor giants in the Galactic halo
• Verf.angabe: G. Cescutti, C. Morossi, M. Franchini, P. Di Marcantonio, C. Chiappini, M. Steffen, M. Valentini, P. François, N. Christlieb, C. Cortés, C. Kobayashi, and E. Depagne
• E-Jahr: 2021
• Jahr: 11 August 2021
• Umfang: 12 S.
• Fussnoten: Gesehen am 09.02.2022
• Titel Quelle: Enthalten in: Astronomy and astrophysics
• Ort Quelle: Les Ulis : EDP Sciences, 1969
• Jahr Quelle: 2021
• Band/Heft Quelle: 654(2021), Artikel-ID A164, Seite 1-12
• ISSN Quelle: 1432-0746
• DOI: doi:10.1051/0004-6361/202141355
• Datenträger: Online-Ressource
• Sprache: eng
• K10plus-PPN: 1789055946

Abstract

<i>Context.<i/> Theoretical results showed the possibility that neutron capture elements were produced in the early Universe by two different sources: a frequent <i>s<i/>-process source hosted by rotating massive stars, and a rare <i>r<i/>-process source hosted most likely by neutron star mergers. The two sources produce barium with different isotopic compositions.<i>Aims.<i/> We aim to investigate the lines of barium in two halo stars, HD 6268 and HD 4306. The spectra present an exquisite quality, both in terms of resolution (<i>R<i/> > 100 000) and signal-to-noise (~400). Due to hyperfine splitting (hfs) effects, barium lines are expected to show slightly different profiles depending on the barium isotopic fraction.<i>Methods.<i/> We applied a standard local thermodynamic equilibrium synthesis of the barium lines. We compared the synthetic results assuming an <i>s<i/>-process isotopic pattern or an <i>r<i/>-process isotopic pattern for the two barium lines for each star that exhibited hfs. We also applied a methodology, less dependent on the accuracy of the theoretical Ba hfs structure, that transforms the lines of HD 4306 into those we would observe if its atmospheric parameter values (i.e. <i>T<i/><sub>eff<sub/>, log <i>g<i/>, micro- and macro-turbulence, <i>V<i/> sin <i>i<i/>, and Ba abundance) were the same as those of HD 6268.<i>Results.<i/> With both methods, our results show that the barium lines with hfs effects of HD 4306 are in agreement with an <i>s<i/>-process composition and the lines in HD 6268 have a different profile, which is most likely linked to the presence of an <i>r<i/>-process isotopic pattern.<i>Conclusions.<i/> Two lines of barium of HD 6268 and HD 4306 seem to confirm the theoretical expectation that both <i>r<i/>-process events and also <i>s<i/>-process contribution by rotating massive stars have polluted the ancient halo of our Galaxy.