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Abstract: We present a measurement of metallicity in the Galactic center QuintupletCluster made using quantitative spectral analysis of two Luminous BlueVariables LBVs. The analysis employs line-blanketed NLTE wind-atmospheremodels 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 ratedegeneracy found in other LBVs and to obtain robust estimates of the He contentof both objects. Our results indicate solar iron abundance and roughly twicesolar abundance in the alpha-elements. These results are discussed within theframework of recent measurements of oxygen and carbon composition in the nearbyArches Cluster and iron abundances in red giants and supergiants within thecentral 30 pc of the Galaxy. The relatively large enrichment of alpha-elementswith respect to iron is consistent with a history of more nucleosynthesis inhigh mass stars than the Galactic disk.



Author: Francisco Najarro, Don F. Figer, D. John Hillier, T. R. Geballe, Rolf P. Kudritzki

Source: https://arxiv.org/







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