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An Abundance Analysis for Five Red Horizontal-Branch Stars in the Extremely Metal-rich Globular Cluster NGC 6553

Cohen, Judith G. and Gratton, Raffaele G. and Behr, Bradford B. and Carretta, Eugenio (1999) An Abundance Analysis for Five Red Horizontal-Branch Stars in the Extremely Metal-rich Globular Cluster NGC 6553. Astrophysical Journal, 523 (2). pp. 739-751. ISSN 0004-637X. doi:10.1086/307765.

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We provide a high-dispersion line-by-line abundance analysis of five red horizontal-branch (HB) stars in the extremely metal-rich Galactic globular cluster NGC 6553. These red HB stars are significantly hotter than the very cool stars near the tip of the giant branch in such a metal-rich globular cluster, and hence their spectra are much more amenable to an abundance analysis than would be the case for red giants. We find that the mean [Fe/H] for NGC 6553 is -0.16 dex, comparable to the mean abundance in the Galactic bulge found by McWilliam & Rich and considerably higher than that obtained from an analysis of two red giants in this cluster by Barbuy and coworkers. The relative abundance for the best-determined α-process element (Ca) indicates an excess of α-process elements of about a factor of 2. The metallicity of NGC 6553 reaches the average of the Galactic bulge and of the solar neighborhood.

Item Type:Article
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URLURL TypeDescription Paper
Cohen, Judith G.0000-0002-8039-4673
Additional Information:© 1999 The American Astronomical Society. Received 1999 February 15; accepted 1999 May 8. Based in large part on observations obtained at the W. M. Keck Observatory, which is operated jointly by the California Institute of Technology and the University of California. We are grateful to Maria Donata Guarnieri and her collaborators for providing access to their HST and IRAC photometry of NGC 6553 prior to publication and for providing finding charts for candidate HB stars from their images and to Jim McCarthy for help during the 1997 observing run. We also thank Beatriz Barbuy and Sergio Ortolani for having provided a copy of their recent paper in advance of publication. The entire Keck/HIRES user community owes a huge debt to Jerry Nelson, Gerry Smith, Steve Vogt, and many other people who have worked to make the Keck Telescope and HIRES a reality and to operate and maintain the Keck Observatory. We are grateful to the W. M. Keck Foundation, and particularly its late president, Howard Keck, for the vision to fund the construction of the W. M. Keck Observatory. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. The work of J. G. C. was partially supported by NSF grant AST-9819614.
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:globular clusters : individual (NGC 6553) - stars : abundances - stars : horizontal-branch
Issue or Number:2
Record Number:CaltechAUTHORS:20190528-134609249
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Official Citation:Judith G. Cohen et al 1999 ApJ 523 739
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:95826
Deposited By: Tony Diaz
Deposited On:28 May 2019 21:26
Last Modified:16 Nov 2021 17:16

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