Theoretical surface abundances of Population I giants

The abundance predictions of standard models of stellar evolution are not in agreement with the observed CNO and other abundance ratios in all giants. The effects are considered of variation of initial composition and mass loss on the abundance ratios of 12C/13C, 12C/14N, 16O/12C, 7Li/H, and 9Be/H in giants. To test these effects, stellar models of 1.0 solar masses, 1.5 solar masses and 2.5 solar masses are evolved with and without mass loss from the zero age main sequence (ZAMS) to the giant branch. Mass loss is treated using a scaled Reimers' mass loss algorithm and an acoustic luminosity algorithm. Sufficient mass loss, if present before the giant branch and/or variation of initial composition could be possible explanations for the anomalous abundances in giants. (author)