OXYGEN ISOTOPIC RATIOS IN COOL R CORONAE BOREALIS STARS

Journal Article · Sat May 01 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/714/1/144· OSTI ID:21448953

Garcia-Hernandez, D A ^[1]; Lambert, David L ^[2]; Rao, N Kameswara ^[3]; Hinkle, Ken H ^[4]; Eriksson, Kjell ^[5]

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1. Instituto de Astrofisica de Canarias (IAC), C/Via Lactea s/n, 38200 La Laguna, Tenerife (Spain)
2. W. J. McDonald Observatory, University of Texas at Austin. 1 University Station, C1400. Austin, TX 78712-0259 (United States)
3. Indian Institute of Astrophysics, Bangalore 560 034 (India)
4. National Optical Astronomy Observatory (NOAO), Tucson, AZ 85726 (United States)
5. Department of Physics and Astronomy, Uppsala University, Box 515, 75120 Uppsala (Sweden)

We investigate the relationship between R Coronae Borealis (RCB) stars and hydrogen-deficient carbon (HdC) stars by measuring precise {sup 16}O/{sup 18}O ratios for five cool RCB stars. The {sup 16}O/{sup 18}O ratios are derived by spectrum synthesis from high-resolution (R {approx} 50, 000) K-band spectra. Lower limits to the {sup 16}O/{sup 17}O and {sup 14}N/{sup 15}N ratios as well as Na and S abundances (when possible) are also given. RCB stars in our sample generally display less {sup 18}O than HdC stars-the derived {sup 16}O/{sup 18}O ratios range from 3 to 20. The only exception is the RCB star WX CrA, which seems to be an HdC-like star with {sup 16}O/{sup 18}O = 0.3. Our result of a higher {sup 16}O/{sup 18}O 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 {sup 12}C and {sup 16}O, may convert an {sup 18}O-rich HdC star into an {sup 18}O-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.

• OSTI ID: 21448953
• Journal Information: Astrophysical Journal, Vol. 714, Issue 1; Other Information: DOI: 10.1088/0004-637X/714/1/144; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABUNDANCE
CARBON
CARBON 12
HYDROGEN
ISOTOPE RATIO
NITROGEN 14
NITROGEN 15
OXYGEN 16
OXYGEN 17
OXYGEN 18
STAR EVOLUTION
WHITE DWARF STARS
CARBON ISOTOPES
DIMENSIONLESS NUMBERS
DWARF STARS
ELEMENTS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
EVOLUTION
ISOTOPES
LIGHT NUCLEI
NITROGEN ISOTOPES
NONMETALS
NUCLEI
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
OXYGEN ISOTOPES
STABLE ISOTOPES
STARS