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Membership of 23 stars towards the bulge globular clusters NGC 6528 and NGC 6553

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Membership of 23 stars towards the bulge globular clusters NGC 6528 and NGC 6553

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Título Membership of 23 stars towards the bulge globular clusters NGC 6528 and NGC 6553
Autor Coelho, Paula
Barbuy, Beatriz
Perrin, Marie-Noel
Idiart, Thais Eunice Pires
Schiavon, Ricardo P.
Ortolani, Sergio
Bica, Eduardo Luiz Damiani
Abstract Low resolution spectra of 23 stars towards the bulge globular clusters NGC 6528 and NGC 6553 are analysed. Radial velocities and atmospheric parameters are derived in order to check their membership in the clusters. Effective temperatures were obtained from photometric data for stars with Teff > 3800 K, whereas for cooler stars, they were derived from equivalent widths of TiO bands. Calibrations of W(TiO) as a function of stellar parameters based on a grid of synthetic spectra are presented. Metallicities were derived from a comparison of the observed spectra to a grid of synthetic spectra. The sample comprises evolutionary stages from the Red Giant Branch to the Horizontal Branch, with parameters in the range 3200 <_ Teff <_ 5000 K and −0.5 <_ log g <_ 2.4. The mean metallicities obtained for NGC 6528 and NGC 6553 are [Fe/H] ≈ −0.5 and −0.7, in both cases with [Mg/Fe] = +0.3; assuming the same overabundance for the α elements O, Mg, Si, S, Ca and Ti, this gives [Z/ZΘ] = −0.25 and −0.45. Membership verification by means of low resolution spectra is a crucial step in preparing targets for high resolution spectroscopy with 8 m class telescopes.
Contido em Astronomy and astrophysics. Les Ulis. Vol. 376, no. 1 (Sept. 2001), p. 136-143
Assunto Aglomerados estelares globulares
Composicao estelar
Espectros estelares
[en] Clusters: globular: NGC 6528, NGC 6553
[en] Stars: abundances
Origem Estrangeiro
Tipo Artigo de periódico
URI http://hdl.handle.net/10183/98500
Arquivos Descrição Formato
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