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<p>The sum of C+N+O in red giants presents interest due to its steady nature during stellar evolution of the star, although the abundance of its components, especially C and N, undergoes significant evolutionary changes. It is shown that there is a pronounced correlation between the total log ε(C+N+O) abundances in red giants and their metallicity index [Fe/H]. The linear relationship between log ε (C + N + O) and [Fe/H] indicates an increase in log ε (C+N+O) from 7.0 with [Fe/H] = -2.5 to 9.2 with [Fe/H] = +0.3, i.e., by more than 2 dex. In contrast, the abundance of (C+N+O) relative to Fe decreases by 0.7 dex over the same [Fe/H] interval. It is shown that the ratio between [(C+N+O)/Fe] and [Fe/H] is almost completely determined by the ratio between [O/Fe] and [Fe/H]; hence, it is confirmed that oxygen is the main contributor to C+N+O. Since current models of Galactic evolution explain the observed dependence of [O/Fe] on [Fe/H] reasonably well, they thereby also explain the observed dependence of [(C+N+O)/Fe] on [Fe/H].</p>

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Total C+N+O Abundances in the Atmospheres of Red Giants of Different Metallicities

  • 期刊论文

  • 发表日期：

    2025年3月1日

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  • L. S. Lyubimkov,
  • D. V. Petrov

摘要

The sum of C+N+O in red giants presents interest due to its steady nature during stellar evolution of the star, although the abundance of its components, especially C and N, undergoes significant evolutionary changes. It is shown that there is a pronounced correlation between the total log ε(C+N+O) abundances in red giants and their metallicity index [Fe/H]. The linear relationship between log ε (C + N + O) and [Fe/H] indicates an increase in log ε (C+N+O) from 7.0 with [Fe/H] = -2.5 to 9.2 with [Fe/H] = +0.3, i.e., by more than 2 dex. In contrast, the abundance of (C+N+O) relative to Fe decreases by 0.7 dex over the same [Fe/H] interval. It is shown that the ratio between [(C+N+O)/Fe] and [Fe/H] is almost completely determined by the ratio between [O/Fe] and [Fe/H]; hence, it is confirmed that oxygen is the main contributor to C+N+O. Since current models of Galactic evolution explain the observed dependence of [O/Fe] on [Fe/H] reasonably well, they thereby also explain the observed dependence of [(C+N+O)/Fe] on [Fe/H].