arXiv 0804.23722008-04-15astro-ph

混合型PG 1159型中央恒星NGC 7094的UV和FUV光谱

UV and FUV spectroscopy of the hybrid PG 1159-type central star NGC 7094

M. Ziegler, T. Rauch, E. Reiff, K. Werner, J. W. Kruk, C. M. Oliveira

备注：: 4 pages, 2 figures

摘要：

以往对三颗PG 1159星（K 1-16，PG 1159-035，NGC 7094）和一颗[WC]-PG 1159过渡星（Abell 78）的铁丰度测定表明，没有任何天体在紫外光谱中显示出铁谱线。恒星通常缺铁至少1德克斯。一个可能的解释是，铁核被中子俘获转化为更重的元素（S过程），然而，铁破坏的程度将比AGB星模型预测的要强得多。但如果氮捕获是正确的解释，那么我们应该观察到反式铁元素的富集。在本文中，我们报告了我们的搜索可能的镍过剩的四个缺铁PG 1159星之一，即中心恒星NGC 7094。我们无法在HST和FUSE光谱中识别任何镍线，并得出结论，镍不是过剩的。可以想象，铁被转化为更重的元素，但由于缺乏原子数据，它们的鉴定受到影响。

英文摘要：

Previous studies aiming at the iron-abundance determination in three PG 1159 stars (K 1-16, PG 1159-035, NGC 7094) and a [WC]-PG 1159 transition star (Abell 78) have revealed that no object shows any iron line in the UV spectrum. The stars are iron-deficient by at least 1 dex, typically. A possible explanation is that iron nuclei were transformed by neutron captures into heavier elements (s-process), however, the extent of the iron-destruction would be much stronger than predicted by AGB star models. But if n-captures are the right explanation, then we should observe an enrichment of trans-iron elements. In this paper we report on our search for a possible nickel overabundance in one of the four Fe deficient PG 1159 stars, namely the central star NGC 7094. We are unable to identify any nickel line in HST and FUSE spectra and conclude that Ni is not overabundant. It is conceivable that iron was transformed into even heavier elements, but their identification suffers from the lack of atomic data.

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