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Light Elements in Main Sequence Stars: Li, Be, B, C, O Ann Merchant Boesgaard Abstract Studies of the rare light elements have been revealing new insights about the structure of field and cluster F and G dwarfs. Keck/HIRES observations show that the Li dip in the Hyades mid-F stars is joined by a Be dip. This Li-Be dip also occurs in other intermediate age clusters, but not in the younger Pleiades. In spite of decreasing Li with decreasing temperatures in the G stars, there is no depletion in Be in the G stars in any of the clusters. For field stars there is little Be depletion in the G stars, but F stars can have Be depletions of more than 2 orders of magnitude. There is a strong correlation of Li and Be between 5900 and 6650 K; the slope from 88 stars is 0.38, with Li declining more rapidly than Be. This is well-matched by models of rotationally-induced mixing. Be and B both show gradual increases with Fe in the disk with a B/Be ratio consistent with production by galactic cosmic rays. A correlation of B and Be depletion has a slope of 0.18. The abundances of several elements have been determined in F and G dwarf stars in the Pleiades, Hyades, and M 67 from Keck/HIRES spectra. The clusters cover a range in age from 70 Myr to 5 Gyr. With a spectral resolution of 48,000 and signal-to-noise ratios of 100-600, the spectra of 20 Pleiades stars, 18 Hyades stars, and 14 M 67 stars have been analyzed. The mean [Fe/H] found for the Pleiades is +0.06 $\pm$0.02, for the Hyades is +0.18 $\pm$0.01, and for M 67 is -0.05 $\pm$0.01. Whereas [C/Fe] and [O/Fe] are near 0.0, i.e. solar, for Hyades and M 67, C is low and O is high in the Pleiades. |