Previous isotopic measurements (see Lambert & Ries 1981) indicate that the observed ratios for G–K giants are of about 10–30, which is significantly lower than the presumed initial (solar) ratio of about 90 (e.g. Moreover, the abundances are not only scaled to stellar nucleosynthesis and mixing, but also to galactic chemical evolution (e.g., Allende Prieto et al. The surface CNO abundances also depend on the mixing process (e.g., Mikolaitis et al. 2018) because carbon will be converted into nitrogen and the 12C/ 13C ratio will be lowered over time by molecular CN processing (also CH and CO). Stellar evolution is traced by the carbon, nitrogen, and oxygen (CNO) abundances and in particular by the 12C/ 13C isotope ratio (e.g., Shetrone 2003 Szigeti et al. Key words: stars: evolution / binaries: spectroscopic / methods: observational / techniques: spectroscopic Our new 12C/ 13C value is significantly lower than the previous value of 27 ± 4 but now agrees better with the recent model prediction of 18.8–20.7. The separated spectrum of the secondary component does not show distinguishable 12CN and 13CN lines because of its vsin i and higher temperature.Ĭonclusions. Our measurement precision is now primarily limited by the spectral-line data and by the grid-step size of the model atmospheres rather than the data. We found that the 12C/ 13C ratio of the primary component of Capella is 17.8 ± 1.9. The isotope ratio was derived with the use of spectrum synthesis from the CN lines at 8004 Å. These average spectra were used to disentangle the two binary components. Signal-to-noise ratios of up to 2 700 were obtained by averaging nightly spectra. We present a new measure of the carbon 12C/ 13C isotope ratio of the primary component of Capella using high-resolution R ≈ 250 000 spectra obtained with the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) with both the Vatican Advanced Technology Telescope (VATT) and the Large Binocular Telescope (LBT). The G0 secondary star is a Hertzsprung-gap giant, and the G8 primary star is thought to be a clump giant.Īims. With spectral types of G8III and G0III, the two components appear at different but distinct stages in their evolution. Leibniz-Institute for Astrophysics Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, GermanyĮ-mail: Capella ( α Aur) is one of the few binaries in the sky with two cool giant stars. Sablowski, Silva Järvinen, Ilya Ilyin and Klaus G. Astronomical objects: linking to databasesĭaniel P. Including author names using non-Roman alphabets.Suggested resources for more tips on language editing in the sciences Punctuation and style concerns regarding equations, figures, tables, and footnotes
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