Metallicity in the Galactic Center:, The Quintuplet cluster

Francisco Najarro(1), Don F. Figer(2), D. John Hillier(3), T. R. Geballe(4), Rolf P. Kudritzki(5)

(1) Instituto de Estructura de la Materia, CSIC, Serrano 121, 29006 Madrid, Spain
(2) Chester F. Carlson Center for Imaging Science, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623
(3) Department of Physics and Astronomy, University of Pittsburgh, 3941 O'Hara Street, Pittsburgh, PA 15260
(4) Gemini Observatory, Hilo, 670 N. A'ohoku Pl., HI 96720
(5) Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822

Paper: ApJ accepted

EPrint Server: 0809.3185


We present a measurement of metallicity in the Galactic center Quintuplet Cluster made using quantitative spectral analysis of two Luminous Blue Variables (LBVs). The analysis employs line-blanketed NLTE wind/atmosphere models fit to high-resolution near-infrared spectra containing lines of H, \HeI, \SiII, \MgII, and \FeII. We are able to break the H/He ratio vs. mass-loss rate degeneracy found in other LBVs and to obtain robust estimates of the He content of both objects. Our results indicate solar iron abundance and roughly twice solar abundance in the alpha -elements. These results are discussed within the framework of recent measurements of oxygen and carbon composition in the nearby Arches Cluster and iron abundances in red giants and supergiants within the central 30 pc of the Galaxy. The relatively large enrichment of alpha -elements with respect to iron is consistent with a history of more nucleosynthesis in high mass stars than the Galactic disk.

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