Oxygen Isotopic Ratios in Cool R Coronae Borealis Stars
2010 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 714, no 1, 144-154 p.Article in journal (Refereed) Published
We investigate the relationship between R Coronae Borealis (RCB) stars and hydrogen-deficient carbon (HdC) stars by measuring precise O-16/O-18 ratios for five cool RCB stars. The O-16/O-18 ratios are derived by spectrum synthesis from high-resolution (R similar to 50,000) K-band spectra. Lower limits to the O-16/O-17 and N-14/N-15 ratios as well as Na and S abundances (when possible) are also given. RCB stars in our sample generally display less O-18 than HdC stars-the derived O-16/O-18 ratios range from 3 to 20. The only exception is the RCB star WX CrA, which seems to be an HdC-like star with O-16/O-18 = 0.3. Our result of a higher O-16/O-18 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 C-12 and O-16, may convert an O-18-rich HdC star into an O-18-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.
Place, publisher, year, edition, pages
2010. Vol. 714, no 1, 144-154 p.
infrared: stars, stars: abundances, stars: atmospheres, stars: chemically peculiar, white dwarfs
Astronomy, Astrophysics and Cosmology
IdentifiersURN: urn:nbn:se:uu:diva-136984DOI: 10.1088/0004-637X/714/1/144ISI: 000276701000012OAI: oai:DiVA.org:uu-136984DiVA: diva2:377796