Carbon isotope ratios and lithium abundances in open cluster giants
Carbon isotope ratios and lithium abundances in open cluster giants
复制标题
疏散星团巨星中的碳同位素比和锂丰度
DOI：
10.1086/168173
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
K. K. Gilroy
中科院分区：
文献类型：
--
作者：
K. K. Gilroy
获得了20多个银河系疏散星团中巨星的CN谱线和Li谱线的高分辨、高信噪比新谱，并测定了它们的C-12/C-13比值和Li丰度。星团的年龄从5000万年到50亿年不等，它们的关闭质量从1个太阳质量到6个太阳质量不等。年龄和关闭质量是通过将理论等时线拟合到星系团色星等图上来确定的。同位素比值和Li丰度与团簇关闭质量的相关性表明：（1）C-12/C-13比值随关闭质量的增加而急剧增加，直到质量约为2.2太阳质量时，比值突然稳定在26附近;（2）一般来说，关闭质量小于2.2太阳质量的老星系团的C-12/C-13比比理论预测值要低得多，而那些关闭质量较大的星系团的C-12/C-13比理论预测值要低得多。（3）Li丰度与集团的截止质量之间没有强的相关性，巨星的Li丰度一般低于理论预测值。讨论了解释观测到的丰度趋势的各种理论。参考文献66篇。«少
New high-resolution, high S/N spectra of CN lines at 8000 A and Li lines at 6707 A have been obtained for giants in about 20 Galactic open clusters and C-12/C-13 ratios and Li abundances determined for these stars. The ages of the clusters vary from about 50 million years to 5 billion years, and their turn-off masses vary from 1 solar mass to about 6 solar masses. The ages and turn-off masses were determined by fitting theoretical isochrones to the cluster color-magnitude diagrams. Correlation of the isotope ratio and the Li abundances with the cluster turn-off masses indicates the following: (1) the C-12/C-13 ratio increases steeply with the turn-off mass until a mass of approximately 2.2 solar masses when the ratio levels off abruptly to a value near 26; (2) older clusters with turn-off masses lower than about 2.2 solar masses in general exhibit C-12/C-13 ratios that are considerably lower than the theoretically predicted values while those with larger turn-off masses show ratios close to standard predictions; and (3) no strong correlation exists between the Li abundances and the cluster turn-off mass, and the Li abundances in giants are, in general, lower than theoretically predicted values. Various theories to explainmore » the observed abundance trends are discussed. 66 refs.« less