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D.H. McNamara (Brigham Young University)
The ages of 16 globular clusters have been inferred from the MvTO (absolute magnitude) values of the clusters. The luminosities of the SX Phe (blue stragglers) variables in the clusters in combination with their P-L relation have been used to fix the MvTO values. We find excellent agreement with the latest isochrones that indicate an age of 11 billion years. The scatter in the data points can be accounted for by errors indicating that the clusters are coeval.
We have also determined the luminosities of the horizontal branches. We found a considerable scatter in the Mv, [Fe/H] relation of the horizontal branches. Since the luminosities of the horizontal branches have been utilized to fix ages by previous investigators, this scatter is probably responsible for the spread in ages reported earlier.