High-Resolution Spectroscopy of Ursa Major Moving Group Stars1;2

We use new and extant literature spectroscopy to address abundances and membership for UMa moving group stars. We rst compare the UMa, Coma, and Hyades H-R diagrams via a homogeneous set of isochrones, and nd that these three aggregates are essentially coeval; this (near) coevality can explain the indistinguishable distributions of UMa and Hyades dwarfs in the chromospheric emission versus color plane. Our spectroscopy of cool UMa dwarfs reveals striking abundance anomalies{trends with Te , ionization state, and excitation potential{ like those recently seen in young cool M34, Pleaides, and Hyades dwarfs. In particular, the trend of rising 7774-based O I abundance with declining Te is markedly subdued in UMa compared to the Pleiades, suggesting a dependence on age or metallicity. Recent photometric metallicity estimates for several UMa dwarfs are markedly low compared to the group's canonical metallicity, and sim-ilar deviants are seen among cool Hyads as well. Our spectroscopy does not con-rm these curious photometric estimates, which seem to be called into questio