The Spectra of Main-Sequence Stars in Galactic Globular Clusters. II. CH and CN Bands in M71

Spectra with a high signal-to-noise ratio of 79 stars that are just below the main-sequence turnoff of M71 are presented. They yield indices for the strength of the G band of CH and the ultraviolet CN band at 3885 Å. These indices are each to first-order bimodal and they are anticorrelated. There are approximately equal numbers of CN-weak/CH-strong and CN-strong/CH-weak main-sequence stars in M71. It is not yet clear whether these star-to-star variations arise from primordial variations or from mixing within a fraction of individual stars as they evolve.