CN and CH Band Strengths of Bright Giants in M3

Abstract

CN and CH band strengths for ten bright red giants in M3 have been measured from archival spectra obtained with the MMT. A CN-CH band strength anticorrelation is confirmed for the program stars together with other stars for which there is published data. This suggests an anticorrelation between carbon and nitrogen abundances with a constant total abundance of carbon plus nitrogen. However, stars which do not follow the CN-CH anticorrelation are also found. The star III-77, which is found to have both strong CN and CH bands, is the most peculiar among them. While three other stars, VZ194, VZ352, and VZ1420, which show both weak CN and CH band strengths could be AGB stars.