红巨星的硫和锌丰度
Sulfur and zinc abundances of red giant stars
摘要：
硫和锌是化学挥发性元素，在研究银河系化学演化过程中起着重要的无贫化示踪作用。然而，关于红巨星已经从主序星演化出来，尽管到目前为止已经报道了一些研究，但可靠的S和Zn丰度测定似乎很困难。在这种情况下，我们试图通过对S I 8694-5、S I 6757和Zn I 6362谱线应用光谱拟合技术，并考虑非LTE效应，确定239颗GK巨星（-0.8 < [Fe/H] < +0.2）的大量样本中这些元素的丰度。此外，还对160颗FGK矮星进行了相似的丰度分析，以供比较。由这些线导出的S和Zn丰度的非LTE校正在大多数情况下< 0.1（-0.2）dex，并且不是非常显著。它揭示了在红巨星的情况下，S I 6757特征作为丰度指标比S I 8694-5更可靠，因为后者遭受了未识别线的混合。最后得到的GK巨星的[S/Fe]-[Fe/H]和[Zn/Fe]-[Fe/H]关系与FGK矮星的关系符合得很好，表明由SI 6757和Zn I 6362谱线可以可靠地确定红巨星的S和Zn丰度。因此，不仅主序星，而且演化的红巨星是有用的跟踪的化学演化历史的S和Zn在磁盘金属丰度的制度，通过使用这些线。
英文摘要：
Sulfur and zinc are chemically volatile elements, which play significant roles as depletion-free tracers in studying galactic chemical evolution. However, regarding red giants having evolved off the main sequence, reliable abundance determinations of S and Zn seem to be difficult despite that a few studies have been reported so far. Given this situation, we tried to establish the abundances of these elements for an extensive sample of 239 field GK giants (-0.8 < [Fe/H] < +0.2), by applying the spectrum-fitting technique to S I 8694-5, S I 6757, and Zn I 6362 lines and by taking into account the non-LTE effect. Besides, similar abundance analysis was done for 160 FGK dwarfs to be used for comparison. The non-LTE corrections for the S and Zn abundances derived from these lines turned out < 0.1(-0.2) dex for most cases and not very significant. It revealed that the S I 6757 feature is more reliable as an abundance indicator than S I 8694-5 for the case of red giants, because the latter suffers blending of unidentified lines. The finally resulting [S/Fe]-[Fe/H] and [Zn/Fe]-[Fe/H] relations for GK giants were confirmed to be in good agreement with those for FGK dwarfs, indicating that S and Zn abundances of red giants are reliably determinable from the S I 6757 and Zn I 6362 lines. Accordingly, not only main-sequence stars but also evolved red giant stars are usable for tracing the chemical evolution history of S and Zn in the regime of disk metallicity by using these lines.
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