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| Paper: |
AGB Stars in Galactic Globular Clusters: Are They Really
Chemically Distinct from Their Fellow RGB and HB Stars? |
| Volume: |
445, Why Galaxies Care about AGB Stars II: Shining Examples and Common Inhabitants |
| Page: |
63 |
| 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 asymptotic giant branch (AGB)
stars in Galactic globular clusters (GCs) suggest that the globular cluster
AGB populations are dominated by cyanogen-weak (CN-weak) stars. This
contrasts strongly with the distributions on the red giant branch (RGB) and
other populations, which often show a 50:50 bimodality in CN band strength.
If this is true 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 globular clusters. We have
obtained medium resolution spectra for about 250 AGB stars across 9
Galactic globular clusters (NGC 1851, NGC 288, NGC 362, NGC 6752, M2, M4,
M5, M10, and 47 Tuc) using the multi-object spectrograph on the
Anglo-Australian Telescope (2df/AAOmega). In this contribution we
present some preliminary findings of the study, in particular for the
second-parameter pair NGC 288 and NGC 362. |
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