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Evidence for Spectral Differences Among 47 Tucanae Turnoff-Region Stars

Published online by Cambridge University Press:  14 August 2015

James E. Hesser
James E. Hesser*
Affiliation:
Herzberg Institute of Astrophysics, Dominion Astrophysical Observatory

Extract

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Evidence that spectral differences observed among globular cluster giant stars with similar V and B-V values persist to fainter absolute magnitudes has been slowly accumulating in the past few years. In the case of 47 Tucanae, photometric evidence for CN strength variations extending to MV=1.5 mag was found from DDO photometry (Hesser, Hartwick and McClure 1976, 1977). Subsequently, CN strength variations at MV=+3.5, i.e., stars at the base of the vertical rise on the subgiant branch, were found by low dispersion spectroscopy (Hesser 1978). Kraft (1979) and collaborators have found evidence for star-to-star variations in NH and CH strengths among subgiant stars below the horizontal-branch level in the metal-poor cluster, M92; and Hesser and Harris (1979) have found CN and CH features to exhibit wide ranges among similar stars in M22, a metal-poor cluster with some apparent similarities to the otherwise uniquely anomalous cluster, Omega Centauri.

Type
August 30 Globular Clusters
Information
Symposium - International Astronomical Union , Volume 85: Star Clusters , 1980 , pp. 453 - 454
Copyright
Copyright © Reidel 1980 

References

Kraft, R.P.: 1979, Ann. Rev. Astron. Astrophy. 17, 309.Google Scholar
Hesser, J.E.: 1978, Astrophys. J. (Letters) 223, L117.Google Scholar
Hesser, J.E., Hartwick, F.D.A., and McClure, R.D.: 1976, Astrophys. J. (Letters) 207, L113.Google Scholar
Hesser, J.E., Hartwick, F.D.A., and McClure, R.D.: 1977, Astrophys. J. Suppl. 33, 471.CrossRefGoogle Scholar
Hesser, J.E. and Harris, G.L.H.: 1979, Astrophys. J. (December).Google Scholar