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首页> 外文期刊>PASJ: Publications of the Astronomical Society of Japan >Photospheric nitrogen abundances and carbon C-12/C-13 ratios of red giant stars
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Photospheric nitrogen abundances and carbon C-12/C-13 ratios of red giant stars

机译：拍摄氮气丰富和碳C-12 / C-13比率的红巨星

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摘要

Nitrogen abundances and carbon isotope ratios (C-12/C-13) in the atmospheres of red giants are known to be influenced by dredge-up of H-burning products, and serve as useful probes to study the nature of evolution-induced envelope mixing. We determined the [N/Fe] and C-12/C-13 ratios for 239 late-G/early-K giant stars by applying the spectrum-fitting technique to the (CN)-C-12 and (CN)-C-13 lines in the similar to 8002-8005 angstrom region, with the aim of investigating how these quantities are related to other similar mixing-affected indicators which were already reported in our previous work. It was confirmed that [N/Fe] values are generally supersolar (typically by several tenths of a dex, though widely differing from star to star), anti-correlated with [C/Fe], and correlated with [Na/Fe], as expected from theory. As seen from their dependence upon stellar parameters, it appears that mixing tends to be enhanced with an increase of stellar luminosity (or mass) and rotational velocity, which is also reasonable from the theoretical viewpoint. In contrast, the resulting C-12/C-13 ratios turned out to be considerably diversified in the range of similar to 5-50 (with a peak around similar to 20), without showing any systematic dependence upon C or N abundance anomalies caused by the mixing of CN-cycled material. It thus appears that our understanding of the photospheric C-12/C-13 ratios in red giants is still incomplete, requiring more observational studies.
机译：已知红巨型大气中的氮丰度和碳同位素比（C-12 / C-13）受到H燃烧产品的疏浚的影响，并用作研究进化诱导的封套性质的有用探针混合。我们通过将光谱拟合技术应用于（CN）-C-12和（CN）-C来确定239个后G /早期K巨星的[N / Fe]和C-12 / C-13比率-13在类似于8002-8005埃地区的线，目的是研究这些数量如何与我们之前的工作中已经报道的其他类似混合的受影响指标有关。确认[N / Fe]值通常是超极性（通常在几十次DEX中，虽然从星形到星星），与[C / Fe]的抗相关，并与[Na / Fe]相关，从理论上预期。从依赖于恒星参数看，似乎随着恒星亮度（或质量）和旋转速度的增加而倾向于增强，这也是从理论上的观点来合理的。相反，所得的C-12 / C-13比率在与5-50相似的范围内变化，在类似于5-50的范围内（与20相似的峰值），而不显示出对C或N丰度异常的任何系统依赖性通过混合CN环循环材料。因此，看来我们对红巨头的拍摄C-12 / C-13比率的理解仍然不完整，需要更多的观察研究。

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