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| Paper: |
The Case of the Missing Cyanogen-rich AGB Stars in Galactic Globular
Clusters |
| Volume: |
458, Galactic Archaeology: Near-Field Cosmology and the Formation of the Milky Way |
| Page: |
205 |
| Authors: |
Campbell, S. W.; Yong, D.; Wylie-de Boer, E. C.; Stancliffe, R. J.; Lattanzio, J. C.; Angelou, G. C.; Grundahl, F.; Sneden, C. |
| Abstract: |
The handful of available observations of AGB stars in Galactic Globular
Clusters suggest that the GC AGB populations are dominated by cyanogen-weak
stars (eg. Norris et al. 1981; Sneden et al. 2000). This contrasts strongly with
the distributions on the RGB (and other) populations, which generally show
a 50:50 bimodality in CN band strength. If this is a real difference then
it presents a serious problem for low metallicity stellar evolution theory
— since such a surface abundance change going from the RGB to AGB is not
predicted by stellar models. However this is only a tentative conclusion,
since it is based on very small AGB sample sizes. To test whether this
problem really exists we have carried out an observational campaign
targeting AGB stars in GCs. Our preliminary results indicate there is
indeed a lack of CN-strong AGB stars. |
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