Oxygen isotopic abundances in evolved stars. IV. Five K giants

Journal Article · Mon Feb 01 04:00:00 EST 1988 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/166047· OSTI ID:7129262

Harris, M J; Lambert, D L; Smith, V V

Oxygen isotopic ratios have been measured in the atmospheres of Alpha UMa, Beta Gem, Beta UMi, Alpha Ari, and Alpha Ser. It is shown that some of the stars in this and previous samples have probably experienced the helium core flash, and that the O-16/O-17 ratios tend to confirm that extramixing of CNO-cycled material into the stars' envelopes has occurred as a result of the flash. The oxygen isotopic ratios are much smaller than the anomalously high ratios seen in stars in the later thermal-pulsing state of evolution. Hence, the anomalous ratios cannot be explained by the helium core flash. It is proposed that they are due to the addition by the third dredge-up mechanism of helium-burned material which is devoid of both O-17 and O-18 and therefore dilutes the O-17 and O-18 abundances acquired during earlier evolutionary stages. This process may also explain the oxygen isotope ratios seen in barium stars, if these are formed by mass transfer from a thermally pulsing binary companion. 57 references.

• Research Organization: Texas Univ., Austin (USA)
• OSTI ID: 7129262
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 325; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
ATMOSPHERES
BINARY STARS
CHEMICAL COMPOSITION
CNO CYCLE
ELEMENTS
FLUIDS
GASES
GIANT STARS
HELIUM
HELIUM BURNING
ISOTOPE RATIO
ISOTOPES
MASS TRANSFER
NONMETALS
OXYGEN ISOTOPES
RARE GASES
STAR BURNING
STAR EVOLUTION
STARS
STELLAR ATMOSPHERES