Bibcode
García-Hernández, D. A.; Lambert, David L.; Kameswara Rao, N.; Hinkle, Ken H.; Eriksson, Kjell
Referencia bibliográfica
The Astrophysical Journal, Volume 714, Issue 1, pp. 144-154 (2010).
Fecha de publicación:
5
2010
Revista
Número de citas
39
Número de citas referidas
34
Descripción
We investigate the relationship between R Coronae Borealis (RCB) stars
and hydrogen-deficient carbon (HdC) stars by measuring precise
16O/18O ratios for five cool RCB stars. The
16O/18O ratios are derived by spectrum synthesis
from high-resolution (R ~ 50, 000) K-band spectra. Lower limits to the
16O/17O and 14N/15N ratios
as well as Na and S abundances (when possible) are also given. RCB stars
in our sample generally display less 18O than HdC
stars—the derived 16O/18O ratios range from
3 to 20. The only exception is the RCB star WX CrA, which seems to be an
HdC-like star with 16O/18O = 0.3. Our result of a
higher 16O/18O ratio for the RCB stars must be
accounted for by a theory of the formation and evolution of HdC and RCB
stars. We speculate that a late dredge-up of products of He burning,
principally 12C and 16O, may convert an
18O-rich HdC star into an 18O-poor RCB star as the
H-deficient star begins its final evolution from a cool supergiant to
the top of the white dwarf cooling track.
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García Hernández