Metallicity in the Galactic Center:
The Quintuplet cluster

Francisco Najarro1, Don F. Figer2, D. John Hillier3, T. R. Geballe4, Rolf P. Kudritzki5

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

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.

Reference: ApJ
Status: Manuscript has been accepted