THE BEHAVIOR OF MAGNESIUM AND SODIUM LINES AMONG GIANTS WITHIN BIMODAL-CN GLOBULAR-CLUSTERS

Echelle spectra have been obtained of Mg I and Na I absorption lines in the wavelength range 5100 angstrom-5600 angstrom for small numbers of CN-strong and CN-weak red giants in the globular clusters NGC 6752, 47 Tuc, and M 22. In the case of the former two clusters, both of which exhibit bimodal CN band strength distributions, the CN-strong stars observed are generally found to exhibit enhanced Na lines but comparable Mg lines in comparison to CN-weak stars of similar (B-V) color and V magnitude. By contrast, a spectrum of a CN-rich giant in M 22 is found to show stronger lines of Na, Mg, Fe, Ti, and Sc than that of a CN-poor giant of comparable magnitude. It is suggested on the basis of available data that the nucleosynthesis products of helium- and carbon-burning reactions were heterogeneously distributed within globular clusters at the time of their formation.