LAMBDA-3883 CN BAND STRENGTHS FOR 238 METAL-POOR HALO GIANTS - EVIDENCE FOR CHEMICAL DIFFERENCES BETWEEN GLOBULAR-CLUSTER AND HALO FIELD GIANTS

Cyanogen band strengths m(CN) for 238 metal-poor giants in the halo field and in 13 globular clusters are tabulated. The distribution of m(CN) in field giants of intermediate metallicity is compared with that of giants of similar evolutionary state in M79, M3, and M13. The field star population is dominated by weak-CN stars. M79 has mostly giants with CN bands of intermediate strength, M3 has relatively few giants with strong CN bands, and M13 is dominated by strong-CN giants. These results add evidence in support of the notion that halo field stars and stars of most globular clusters differ chemically even at equivalent [Fe/H]. In the spectra of giant stars in the very metal-poor clusters M15 and M92, CN bands tend to disappear, and become noticeable only in stars having exceptionally large nitrogen abundances.