Chemical composition and evolutionary state of the early R stars

Journal Article · Tue May 01 00:00:00 EDT 1984 · Astrophys. J., Suppl. Ser.; (United States)

DOI:https://doi.org/10.1086/190946· OSTI ID:6654507

Dominy, J F

A sample of 11 stars classified R0-R5 has been analyzed to determine (i) iron-peak metal abundances, (ii) abundances of elements produced by the s-process, (iii) the light element abundances (C,N, and O), and (iv)= the carbon isotopic ratio /sup 12/C//sup 13/C. Abundances are reported relative to the Sun. With the expection of HD 100764, which has an iron abundance 0.6 dex lower than the Sun's, the iron abundance of 10 stars is near solar. The s-process elements have no demonstrable enhancement in the sample, unlike the Ba II stars of the same temperature and the cooler carbon stars. The enhancement of carbon relative to the G-K giants found in the analysis of eight stars is 0.7 dex, with one star having Croughly-equal O (HD 113801), while another star (HD 95405) is probably not a carbon star (C/O = 0.87). Relative to the ordinary G-K giants, nitrogen is enhanced by a small amount (0.2 dex). In contrast, oxygen has nearly the value found in the Sun and in normal giants, except in the case of HD 100764 where O is probably as underabundant as Fe. The /sup 12/C//sup 13/C ratio ranges for near 4 to 14 for nine stars, indicating an enrichment of /sup 13/C with respect to the majority of faint giants. For HD 156074 the oxygen isotopic ratios /sup 16/O//sup 17/O and /sup 16/O//sup 18/O do not have detectable departures from the solar system values. The lack of oxygen depletion indicates that the CNO cycle operating near equilibrium is not responsible for the fact that C/O>1 in these stars. Based on the early R stars' position in the H-R diagram, their space number densities, and their enhanced carbon abundances, it is here suggested that they result from mixing at the time of, or closely following, the helium core flash.

• Research Organization: Department of Astronomy, University of Texas at Austin
• OSTI ID: 6654507
• Journal Information: Astrophys. J., Suppl. Ser.; (United States), Vol. 55:1
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CARBON STARS
CHEMICAL COMPOSITION
NUCLEOSYNTHESIS
STAR EVOLUTION
ABUNDANCE
BARIUM IONS
CARBON
CARBON 13
CARBON 14
CARBON BURNING
CNO CYCLE
NEUTRONS
NITROGEN
NITROGEN 13
NITROGEN 14
OXYGEN
OXYGEN 16
OXYGEN 17
OXYGEN 18
R PROCESS
S PROCESS
BARYONS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
CARBON ISOTOPES
CHARGED PARTICLES
ELECTRON CAPTURE RADIOISOTOPES
ELEMENTARY PARTICLES
ELEMENTS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
FERMIONS
HADRONS
IONS
ISOTOPES
LIGHT NUCLEI
MAIN SEQUENCE STARS
MINUTES LIVING RADIOISOTOPES
NITROGEN ISOTOPES
NONMETALS
NUCLEI
NUCLEONS
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
OXYGEN ISOTOPES
RADIOISOTOPES
STABLE ISOTOPES
STAR BURNING
STARS
SYNTHESIS
YEARS LIVING RADIOISOTOPES
640102* - Astrophysics & Cosmology- Stars & Quasi-Stellar
Radio & X-Ray Sources