NOAO >   Observing Info >   Approved Programs >   2006A-0391

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Proposal Information for 2006A-0391


PI: Kenneth Hinkle, NOAO, hinkle@noao.edu
Address: NGSC, P.O. Box 26732, Tucson, AZ 85726, USA

CoI: David Lambert, University of Texas
CoI: Verne Smith, NOAO
CoI: Thomas Lebzelter, University of Vienna

Title: The HdC stars as recently merged white dwarf binaries

Abstract: The hydrogen-deficient carbon star HD 137613 has been reported by Clayton et al. (2005) to have the extraordinary isotopic ratio ^16O/^18O ~ 0.8. The solar system ratio is ~500 and carbon stars typically have yet larger ratios. The explanation proposed for the ^16O/^18O value observed in HD 137613 is that the HdC stars are recently merged white dwarf binaries. The observed supergiant HdC star is a transient post-merger phase. If so, we have the rare opportunity to see helium-burning shell products in a low gravity stellar environment. To test this model we propose to measure the CNO elemental abundances for HD 137613 as well as the other four hydrogen- deficient carbon stars. Comparison of the measure abundances with models will lead to considerable insight into stellar mergers and nucleosynthesis.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



NOAO >   Observing Info >   Approved Programs >   2006A-0391

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