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L. Origlia (A.O. Bologna), R.M. Rich (UCLA), S.M. Castro (IPAC)
Using the NIRSPEC spectrograph at Keck II, we have obtained echelle spectra covering the range 1.5-1.8\mu \rm m for 2 of the brightest giants in Liller~1 and NGC~6553, old metal rich globular clusters in the Galactic bulge. We also report a preliminary analysis for two giants in the obscured bulge globular cluster Ter 5. We use spectrum synthesis for the abundance analysis, and find \rm [Fe/H]=-0.3±.2 and \rm [O/H]=+0.3±0.1 (from the OH lines) for the giants in Liller 1 and NGC 6553. We measure strong lines for the alpha elements Mg, Ca, and Si, but the lower sensitivity of these lines to abundance permits us to only state a general \rm [\alpha/Fe]=+0.3±.2 dex. The composition of the clusters is similar to that of field stars in the bulge and is consistent with a scenario in which the clusters formed early, with rapid enrichment. Our iron abundance for NGC~6553 is poorly consistent with either the low or the high values recently reported in the literature, unless unusally large, or no \alpha-element enhancements are adopted, respectively. We will also present an abundance analsyis for 2 giants in the highly reddened bulge cluster Ter 5, which appears to be near the Solar metallicity.
R. Michael Rich acknowledges finacial support from grant AST-0098739, from the National Science Foundation. Data presented herein were obtained at the W.M.Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors gratefully acknowledge those of Hawaiian ancestry on whose sacred mountain we are privileged to be guests. Without their generous hospitality, none of the observations presented would have been possible.
The author(s) of this abstract have provided an email address for comments about the abstract: rmr@astro.ucla.edu