Spectroscopy of red giants in the globular cluster Palomar 5

Spectra have been obtained of the brightest red giants in the globular cluster Palomar 5. A measurement of the strength of the Ca II H and K lines indicates that the metal abundance is [Fe/H] = -1.4. The Pal 5 giants exhibit striking variations in the λ3883 CN band strength, which appear to anticorrelate with the strength of the λ4300 CH feature with the exception of one giant which may be a weak G band star. Although such variations have been found in a number of inner halo globular clusters, their existence within Pal 5 is significant because of its very low mass (≡1.3×104M_sun;). Some implications of this result with regard to the origin of these variations are discussed.