在PG1159恒星中搜索铁、镍和氟
Search For Iron, Nickel, and Fluorine in PG1159 Stars
摘要：
PG 1159恒星缺铁的一个可能来源是铁核上的中子俘获。镍过剩将证实这一想法。因此，我们正在寻找PG 1159恒星中的镍线。主要目标是相对较冷的物体，因为Ni VI是主要的电离阶段，并且该离子的谱线可以通过紫外观测获得。我们在FUSE观测到的最冷的PG 1159恒星（PG 1707 +427，Teff = 85，000 K）中没有发现这样的线，并得出结论，镍丰度没有增加。因此，PG 1159恒星的铁缺乏仍然无法解释。此外，我们提出的混合PG 1159星NGC 7094和[WC]-PG 1159过渡型对象阿贝尔78的风分析的结果，以获得F丰度从F VI 1139.5埃线。在这两种情况下，我们发现F过剩，与许多PG 1159星的光球分析结果一致。令人惊讶的是，我们在NGC 7094中发现了非常低的O丰度。
英文摘要：
A possible origin of the iron-deficiency in PG1159 stars could be neutron captures on Fe nuclei. A nickel overabundance would corroborate this idea. Consequently we are looking for nickel lines in PG1159 stars. Prime targets are relatively cool objects, because Ni VI is the dominant ionisation stage and the spectral lines of this ion are accessible with UV observations. We do not find such lines in the coolest PG1159 star observed by FUSE (PG1707+427, Teff = 85,000 K) and conclude that the nickel abundance is not enhanced. Hence, the Fe-deficiency in PG1159 stars remains unexplained. In addition, we present results of a wind analysis of the hybrid-PG1159 star NGC 7094 and the [WC]-PG1159 transition-type object Abell 78 in order to derive F abundances from the F VI 1139.5 Angstrom line. In both cases, we find F overabundances, in agreement with results of photospheric analyses of many PG1159 stars. Surprisingly, we find indications for a very low O abundance in NGC 7094.
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