CHEMICAL ABUNDANCES FOR F-LUMINOSITY AND G-LUMINOSITY CLASS-II STARS

Stellar parameters and abundances for a sample of 38 F/G held bright giants have been determined based on high-resolution and high signal-to-noise KPNO coude spectra. This study was designed to complement CNO abundance studies of supergiants and giants which bracket the present stars in mass. The pertinent results of the present study are: The bright giants have [Fe/H] ratios which are solar and are in good agreement with the [Fe/H] ratios found in supergiants and giants. The lithium abundances ate diluted in most stars with respect to the canonical interstellar disk value and the lithium abundances correlate with effective temperature. The CNO abundances of all of the stars show the effects of nuclear processing though to different degrees: the stars are carbon deficient and nitrogen enhanced. The [O/Fe] ratio in these stars in subsolar with an average value of similar to-0.3 dex. The [O/Fe] ratio correlates with the [C/Fe] ratio. All of these effects are also present in the Li and CNO abundances of supergiants and giants. The implication of these results is that the standard model of stellar mixing is deficient and that new evolutionary models are needed incorporating such effects as rotationally driven mixing and diffusion. (C) 1995 American Astronomical Society.