Abundance differences among G and K giants

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:6596015

Challener, S L.M.

Effective temperatures and surface gravities have been derived for 52 G and K giants using model atmosphere. Of these, 33 have been called Very Strong-Lined (or VSL) stars primarily because of their CN line strength. The author finds that when compared to normal stars, the VSL stars show a mean iron overabundance of 0.15 dex. Contrary to earlier suggestions, none of the heavier elements (Z > 10) appear selectivity enhanced. Red giants are believe to undergo mixing, thereby driving the surface abundances towards those of the stellar interior. Carbon, nitrogen and oxygen abundances are most sensitive to mixing as they are produced through nucleosynthesis at various depths beneath the star's surface. The CNO abundances (normalized to the iron abundances) of the VSLs appear on average to be normal for G and K giants. This result suggests that the strong CN absorption seen in VSLs is not the result of unusual mixing. Their general overabundance of metal appears instead to be innate, presumably reflecting the metallicity of the gaseous clouds from which they formed. This should be settled once the appropriate number of VSL dwarfs is found. The deviation from the normal population of giants are rather small, however, and certainly not of the magnitude envisioned by Spinrad and Taylor (1969). It is likely the VSLs are merely the stars lying in the tail of the normal abundance distribution.

• Research Organization: Case Western Reserve Univ., Cleveland, OH (USA)
• OSTI ID: 6596015
• 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
CARBON
CHEMICAL COMPOSITION
DWARF STARS
ELEMENT ABUNDANCE
ELEMENTS
GIANT STARS
GRAVITATION
IRON
METALS
MIXING
NITROGEN
NONMETALS
NUCLEOSYNTHESIS
OXYGEN
RED GIANT STARS
STARS
STELLAR ATMOSPHERES
SYNTHESIS
TRANSITION ELEMENTS