CNO ABUNDANCES OF HYDROGEN-DEFICIENT CARBON AND R CORONAE BOREALIS STARS: A VIEW OF THE NUCLEOSYNTHESIS IN A WHITE DWARF MERGER

摘要: We present high-resolution (R ~ 50, 000) observations of near-IR transitions CO and CN the five known hydrogen-deficient carbon (HdC) stars four R Coronae Borealis (RCB) stars. perform an abundance analysis these by using spectrum synthesis state-of-the-art MARCS model atmospheres for cool Our confirms reports Clayton colleagues that those HdC exhibiting lines in their RCB star S Aps are strongly enriched 18O (with 16O/18O ratios ranging from 0.3 to 16). Nitrogen form 14N 12C, respectively. Elemental abundances CNO obtained C I, C2, CN, lines. Difficulties deriving discussed. Abundances Na I obtained. isotopic suggest may be related objects, they probably formed a merger He white dwarf with C-O dwarf.