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| Paper: |
On the Controversy over the Oxygen Abundances of the Oldest Stars |
| Volume: |
293, 3D Stellar Evolution |
| Page: |
190 |
| Authors: |
Kraft, R. P. |
| Abstract: |
Accurate oxygen abundances ([O/Fe]-ratios) of old, metal-poor stars are required as input data for several fundamental problems. Among these are (1) the hydrogen burnout ages of globular cluster main sequence turnoff stars, (2) comparison of predicted and observed values of [O/Fe] in old stars, as a test of nucleosynthesis in Type II supernovae, and (3) delineation of the change in [O/Fe]-ratios as a function of luminosity among globular cluster and halo field stars, as a test of theories of stellar evolution. We describe the four spectroscopic sources of O abundance in such stars, beginning with (1) the classically-employed [O I] doublet at 6300/ 6364 A, on through (2) the permitted O I triplet at 7772/7774/7775 A, (3) the near-IR OH vibration-rotation bands in the 1.5-1.7 micron region, and (4) the near-UV OH electronic transition bands (3080-3300 A). Each indicator has advantages and disadvantages, but analysis based on conventional 1D LTE model atmospheres leads to discrepancies among the indicators. The introduction of more realistic 3D models of the kind computed by Asplund and associates gives promise of resolving the issue, but difficulties remain. |
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