The present-day chemical composition of the SMC from UVES spectra of the sharp-lined, B-type dwarf AV 304
The present-day chemical composition of the SMC from UVES spectra of the sharp-lined, B-type dwarf AV 304
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根据锐线 B 型矮星 AV 304 的 UVES 光谱得出的 SMC 的当前化学成分
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
P. Dufton
中科院分区：
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作者：
W. Rolleston;K. Venn;E. Tolstoy;P. Dufton
本文介绍了小麦哲伦星云(SMC)中B型主序星AV304的高分辨率VLT/UVES光谱观测。这些光谱已经使用LTE模型大气技术进行了分析，以获得恒星大气参数和化学成分。由于AV304位于氢燃烧主序带内，其化学成分应该反映SMC星际介质(ISM)的化学成分。对一颗银河系比较星进行了详细的逐行差分分析。在AV304中，a过程元素O、Si和S普遍缺乏-0.43+/-0.05Dex，铁也具有类似的低丰度。氧可能相对过剩，与0.1Dex相似，而碳和铝相对不足，与0.2Dex相似。氮的丰度很低(相对于氢为-1.2Dex，相对于铁为-0.7Dex)。这被解释为在SMC中抑制了CNO双循环。此外，大量的氮缺乏与SMC H II区的发现非常一致。事实上，这是恒星天体物理学的第一次--证实了SMC ISM的低基线氮组成(即。12+对数(N/H)，类似于6.66+/-0.10Dex)。
High-resolution spectroscopic VLT/UVES observations are presented for the B-type main-sequence star, AV 304, in the Small Magellanic Cloud (SMC). These spectra have been analysed using LTE model-atmosphere techniques, to derive stellar atmospheric parameters and chemical compositions. As AV 304 is located within the hydrogen burning main-sequence band, its chemical composition should reflect that of the SMC interstellar medium (ISM). A detailed line-by-line differential analysis has been undertaken relative to a Galactic comparison star. A general metal deficiency for the a-process elements O, Si & S of -0.43 +/- 0.05 dex is found for AV 304, with iron having a similar underabundance. Oxygen may be relatively over-abundant by similar to0.1 dex and carbon and aluminium underabundant by similar to0.2 dex. A large nitrogen underabundance (of -1.2 dex relative to hydrogen and -0.7 dex relative to iron) is found. This is interpreted in terms of the CNO bi-cycle having been suppressed in the SMC. Furthermore, the large nitrogen deficiency is in excellent agreement with that found for SMC H II regions. Indeed, this represents a first for stellar astrophysics - confirming the low base-line nitrogen composition of the SMC ISM (viz. 12+log(N/H) similar to 6.66 +/- 0.10 dex).