/sup 12/C//sup 13/C ratios in stars ascending the giant branch the first time

Journal Article · Thu Jan 15 04:00:00 EST 1976 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/154097· OSTI ID:7354806

Dearborn, D S.P.; Eggleton, P P; Schramm, D N

Stellar evolution calculations were carried out for 1 M/sub sun/ and 2 M/sub sun/ red giants in order to understand the observed /sup 12///sup 13/C ratios. Although very low values of 5 to 7 in some red supergiants can be understood in terms of thermally unstable helium shell burning models, there remains a problem of moderately low values (10 to 20) in stars not luminous enough for this process. In addition to the standard mixing at the base of the giant branch, which can give /sup 12/C/sup 13/C ratios in the region of 25 to 30, we consider: variation in initial composition; meridional mixing; mass loss; zero-age composition gradient; mixing during the helium flash; and instability of the hydrogen-burning shell. Of these, only the mass loss mechanism and the hydrogen shell instability produce values below approx.20. (AIP)

• Research Organization: Department of Astronomy, University of Texas
• OSTI ID: 7354806
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 203:2; 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
CARBON 12
CARBON 13
CARBON ISOTOPES
CHEMISTRY
COSMOCHEMISTRY
CRYOGENIC FLUIDS
ELEMENTS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
FLUIDS
GIANT STARS
HELIUM
HYDROGEN
INSTABILITY
ISOTOPE RATIO
ISOTOPES
LIGHT NUCLEI
LUMINOSITY
MASS
NONMETALS
NUCLEI
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RARE GASES
RED GIANT STARS
STABLE ISOTOPES
STAR EVOLUTION
STARS