CN and CH inhomogeneities among lower giant branch stars in M71

Spectra obtained with the 2. 5-m Isaac Newton Telescope show that a bimodal distribution of both 3883- and 4215-Å CN band strengths exists among M71 lower giant branch stars with magnitudes in the range |+ 0. 8 MV 2. 4|⁠. The strength of the 4300-Å CH band is found to be anticorrelated with the CN band strength. Enhanced CN bands are found among fewer than half of the evolved stars in M71, indicating that it has one of the lowest incidences of CN-enhanced giants of any globular cluster observed to date. The data provide evidence that, in addition to the very pronounced CN band strength differences seen between the CN-weak and CN-strong groups of giants, intrinsic CN inhomogeneities exist internal to both of these groups.