The chemical composition of stars in globular clusters.

Detailed analyses for stars in seven globlar cluster six to thirteen kpc distant from the center of the Galaxy are presented. The observational data are shown and questions of membership and selection effects are discussed. The details of fine analysis and the determination of model atmosphere parameters are described and the chemical composition of the stars is derived. The effects of uncertainties in the model atmospheres on the derived abundances are considered. The results are combined with those of other investigators to obtain a set of cluster compositions for all globulars which have been analyzed at high resolution. These abundances are compared with lower resolution data and with other globular cluster metallicity indicators to derive new calibrations for some of these systems, with particular attention to metal-rich systems. The oxygen abundance in globular clusters is examined in detail and the results are compared to the halo field population. The implications of the results for various parameters that may determine the structure of cluster horizontal branches are discussed.