ANTICORRELATED CN AND CH VARIATIONS ON THE 47-TUCANAE MAIN-SEQUENCE TURNOFF

Observations of CN and CH band strengths among a random sample of main -sequence turnoff stars (+3.9<M(V)<+4.6) in the globular cluster 47 Tu c (NGC 104, C0021-723) were made with the CTIO Argus fiber spectrograp h for the purpose of determining the ratio of CN-strong to CN-weak sta rs and investigating the behavior of CH relative to CN. Of the 20 turn off stars, 12 were found to be CN-strong while 8 appear to be CN-weak. This ratio of CN-strong to CN-weak stars is similar to the ratios fou nd among the more luminous 47 Tuc stars and implies little change in t he overall distribution of CN with evolutionary state, although the pr esent sample size is small. A general anticorrelation between CN and C H is also observed in that the CN-weak main-sequence stars all (with o ne possible exception) exhibit strong CH bands-a trend similar to that found among the brighter stars. That these variations occur among suc h relatively unevolved stars and that the overall CN distribution appe ars to be independent of evolutionary state presents serious challenge s to stellar interior mixing theories of their origin. We therefore su ggest that at least some component of the C and N abundance inhomogene ities observed among the brighter (more evolved) stars of this cluster appears to have been established prior to the commencement of evoluti on up the red giant branch.