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E. A. Barrett, A. M. Boesgaard (U. Hawaii), J. R. King (UNLV), C. P. Deliyannis (Indiana U.)
We have embarked on a study of the composition of solar-type stars in the open cluster M67. The metallicity and age of M67 are comparable to those of the Sun. By selecting stars of similar temperatures to the sun, we have basically selected solar twins to analyze. We have made observations of 14 of these solar twins with the Keck I telescope with HIRES at a resolution of 45,000. The spectra cover the region of 5700 - 8100 A with signal-to-noise ratios of 70-140. We present the results of the abundance analysis of Fe, Li, C and O in these stars. We derive an over-all value for the cluster metallicity and for the alpha elements C and O. However, we have found star-to-star variations in the Li content. Li depletion is common, as is seen in the sun, but some stars have significant Li remaining in their atmospheres. By studying cluster stars we can rule out several parameters as the cause of the Li variations since all the stars have similar values for age, composition, temperature, luminosity, mass, evolutionary history.