HdC和RCB星的CNO丰度：对白矮星合并中核合成的看法
CNO abundances of HdC and RCB stars: a view of the nucleosynthesis in a white dwarf merger
摘要：
我们提出了高分辨率（R~ 50，000）的近红外光谱的CO和CN的五个已知的缺氢碳（HdC）星和四个R Coronae Borealis（RCB）星的过渡的观测。我们执行这些恒星的丰度分析，通过使用光谱合成和国家的最先进的MARCS模型的气氛冷缺氢星。我们的分析证实了Clayton及其同事的报告，即在光谱中显示CO线的HdC星和冷的RCB星S Aps强烈富集18 O（16 O/18 O比值为0.3至16）。氮和碳分别以14 N和12 C的形式存在。CNO的元素丰度从Cl、C2、CN和CO线获得。讨论了碳丰度计算中的困难。获得了NaI线的Na丰度和SI线的S丰度。元素和同位素CNO丰度表明HdC和RCB星可能是相关的天体，它们可能是由一颗He白矮星和一颗C-O白矮星合并而成的。
英文摘要：
We present high-resolution (R~50,000) observations of near-IR transitions of CO and CN of the five known hydrogen-deficient carbon (HdC) stars and four R Coronae Borealis (RCB) stars. We perform an abundance analysis of these stars by using spectrum synthesis and state-of-the-art MARCS model atmospheres for cool hydrogen-deficient stars. Our analysis confirms reports by Clayton and colleagues that those HdC stars exhibiting CO lines in their spectrum and the cool RCB star S Aps are strongly enriched in 18O (with 16O/18O ratios ranging from 0.3 to 16). Nitrogen and carbon are in the form of 14N and 12C, respectively. Elemental abundances for CNO are obtained from CI, C2, CN, and CO lines. Difficulties in deriving the carbon abundance are discussed. Abundances of Na from NaI lines and S from SI lines are obtained. Elemental and isotopic CNO abundances suggest that HdC and RCB stars may be related objects and that they probably formed from a merger of a He white dwarf with a C-O white dwarf.
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