来自多重态3的晕星1045 nm处的硫丰度
Sulphur abundances in halo stars from Multiplet 3 at 1045 nm
摘要：
硫是一种挥发性的阿尔法元素，不会被锁定在星际介质（ISM）中的尘埃颗粒中。因此，在比较ISM和恒星大气时，它的丰度不需要进行尘埃损耗的校正。贫金属恒星的光球层中硫的丰度是一个有争议的问题：根据一些作者，[S/Fe]与[Fe/H]在低金属丰度时形成一个平台，而根据其他研究，有一个大的分散或可能是双峰分布。在贫金属的恒星中，硫可以通过其在920 nm处的Mul.1谱线检测到，但这个范围被大地散射严重污染，并且多重谱线中的一条被氢的Paschen zeta谱线混合。我们研究了使用Mult的可能性。3（在1045 nm处）用于推导硫丰度，因为这个范围，现在可以在VLT上用红外光谱仪CRIRES观察到，很少受到大地吸收的污染，至少在贫金属恒星中不受混合物的影响。考虑到NLTE校正和3D效应，我们比较了来自多重态1和3的丰度。在这里，我们提出了一个样本的四颗恒星的结果，虽然分散是不太明显，比以前的分析，我们不能找到一个平台[S/Fe]，并确认分散的硫丰度在低金属。
英文摘要：
Sulphur is a volatile alpha-element which is not locked into dust grains in the interstellar medium (ISM). Hence, its abundance does not need to be corrected for dust depletion when comparing the ISM to the stellar atmospheres. The abundance of sulphur in the photosphere of metal-poor stars is a matter of debate: according to some authors, [S/Fe] versus [Fe/H] forms a plateau at low metallicity, while, according to other studies, there is a large scatter or perhaps a bimodal distribution. In metal-poor stars sulphur is detectable by its lines of Mult.1 at 920 nm, but this range is heavily contaminated by telluric absorptions, and one line of the multiplet is blended by the hydrogen Paschen zeta line. We study the possibility of using Mult. 3 (at 1045 nm) for deriving the sulphur abundance because this range, now observable at the VLT with the infra-red spectrograph CRIRES, is little contaminated by telluric absorption and not affected by blends at least in metal-poor stars. We compare the abundances derived from Multiplets 1 and 3, taking into account NLTE corrections and 3D effects. Here we present the results for a sample of four stars, although the scatter is less pronounced than in previous analysis, we cannot find a plateau in [S/Fe], and confirm the scatter of the sulphur abundance at low metallicity.
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