Bibcode
García-Hernández, D. A.; Hinkle, K. H.; Lambert, David. L.; Eriksson, K.
Referencia bibliográfica
The Astrophysical Journal, Volume 696, Issue 2, pp. 1733-1754 (2009).
Fecha de publicación:
5
2009
Revista
Número de citas
35
Número de citas referidas
32
Descripción
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 C I,
C2, CN, and CO lines. Difficulties in deriving the carbon
abundance are discussed. Abundances of Na from Na I lines and S from S I
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 an He white dwarf with a C-O white dwarf.
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