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Session 13 - Stellar Spectra.
Display session, Wednesday, January 07
Exhibit Hall,
We present oxygen abundances for a sample of eight field dwarf stars with -0.9 < [Fe/H] < -0.5, which are more metal-rich than the traditional halo-disk boundary but have kinematics typical of metal-poor halo stars. The observed [O/Fe] abundances show a scatter which is larger than the expected observational errors. Consideration of these and published O/Fe determinations indicates a substantial range of [O/Fe] in the range -1.2 < [Fe/H] < -0.5, with no clear correlation with kinematics. If the O/Fe ratio is indicative of the chemical evolution time scale, these data suggest that no single time scale is sufficient to characterize the evolution of the metal-rich halo or the metal-poor disk, nor is there a clear boundary in time between the two.
