High-resolution abundance analysis of four red giants in the globular cluster NGC 6558
Autor(a) principal: | |
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Data de Publicação: | 2018 |
Outros Autores: | , , , , , , , , , |
Tipo de documento: | Artigo |
Idioma: | eng |
Título da fonte: | Repositório Institucional da UFRGS |
Texto Completo: | http://hdl.handle.net/10183/203997 |
Resumo: | Context. NGC 6558 is a bulge globular cluster with a blue horizontal branch (BHB), combined with a metallicity of [Fe/H] ≈ −1.0. It is similar to HP 1 and NGC 6522, which could be among the oldest objects in the Galaxy. Element abundances in these clusters could reveal the nature of the first supernovae. Aims. We aim to carry out detailed spectroscopic analysis for four red giants of NGC 6558, in order to derive the abundances of the light elements C, N, O, Na, Al, the α-elements Mg, Si, Ca, Ti, and the heavy elements Y, Ba, and Eu. Methods. High-resolution spectra of four stars with FLAMES-UVES at VLT UT2-Kueyen were analysed. Spectroscopic parameter-derivation was based on excitation and ionization equilibrium of Fe I and Fe II. Results. This analysis results in a metallicity of [Fe/H] = − 1.17 ± 0.10 for NGC 6558. We find the expected α-element enhancements in O and Mg with [O/Fe] = +0.40, [Mg/Fe] = +0.33, and low enhancements in Si and Ca. Ti has a moderate enhancement of [Ti/Fe] = +0.22. The r-element Eu appears very enhanced with a mean value of [Eu/Fe] = +0.63. The first peak s-elements Y and Sr are also enhanced, these results have however to be treated with caution, given the uncertainties in the continuum definition; the use of neutral species (Sr I, Y I), instead of the dominant ionized species is another source of uncertainty. Ba appears to have a solar abundance ratio relative to Fe. Conclusions. NGC 6558 shows an abundance pattern that could be typical of the oldest inner bulge globular clusters, together with the pattern in the similar clusters NGC 6522 and HP 1. They show low abundances of the odd-Z elements Na and Al, and of the explosive nucleosynthesis α-elements Si, Ca, and Ti. The hydrostatic burning α-elements O and Mg are normally enhanced as expected in old stars enriched with yields from core-collapse supernovae, and the iron-peak elements Mn, Cu, Zn show low abundances, which is expected for Mn and Cu, but not for Zn. Finally, the cluster trio NGC 6558, NGC 6522, and HP 1 have relatively high abundances of first-peak heavy elements, variable second-peak element Ba, and the r-element Eu is enhanced. The latter is particularly high in NGC 6558. |
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Barbuy, BeatrizMuniz, Leone V.Ortolani, SergioErnandes, HeitorDias, Bruno Moreira de SouzaSaviane, IvoKerber, Leandro de OliveiraBica, Eduardo Luiz DamianiPérez Villegas, Maria de Los AngelesRossi, Luca JamesHeld, Enrico V.2019-12-28T04:03:15Z20180004-6361http://hdl.handle.net/10183/203997001109427Context. NGC 6558 is a bulge globular cluster with a blue horizontal branch (BHB), combined with a metallicity of [Fe/H] ≈ −1.0. It is similar to HP 1 and NGC 6522, which could be among the oldest objects in the Galaxy. Element abundances in these clusters could reveal the nature of the first supernovae. Aims. We aim to carry out detailed spectroscopic analysis for four red giants of NGC 6558, in order to derive the abundances of the light elements C, N, O, Na, Al, the α-elements Mg, Si, Ca, Ti, and the heavy elements Y, Ba, and Eu. Methods. High-resolution spectra of four stars with FLAMES-UVES at VLT UT2-Kueyen were analysed. Spectroscopic parameter-derivation was based on excitation and ionization equilibrium of Fe I and Fe II. Results. This analysis results in a metallicity of [Fe/H] = − 1.17 ± 0.10 for NGC 6558. We find the expected α-element enhancements in O and Mg with [O/Fe] = +0.40, [Mg/Fe] = +0.33, and low enhancements in Si and Ca. Ti has a moderate enhancement of [Ti/Fe] = +0.22. The r-element Eu appears very enhanced with a mean value of [Eu/Fe] = +0.63. The first peak s-elements Y and Sr are also enhanced, these results have however to be treated with caution, given the uncertainties in the continuum definition; the use of neutral species (Sr I, Y I), instead of the dominant ionized species is another source of uncertainty. Ba appears to have a solar abundance ratio relative to Fe. Conclusions. NGC 6558 shows an abundance pattern that could be typical of the oldest inner bulge globular clusters, together with the pattern in the similar clusters NGC 6522 and HP 1. They show low abundances of the odd-Z elements Na and Al, and of the explosive nucleosynthesis α-elements Si, Ca, and Ti. The hydrostatic burning α-elements O and Mg are normally enhanced as expected in old stars enriched with yields from core-collapse supernovae, and the iron-peak elements Mn, Cu, Zn show low abundances, which is expected for Mn and Cu, but not for Zn. Finally, the cluster trio NGC 6558, NGC 6522, and HP 1 have relatively high abundances of first-peak heavy elements, variable second-peak element Ba, and the r-element Eu is enhanced. The latter is particularly high in NGC 6558.application/pdfengAstronomy and astrophysics. Les Ulis. Vol. 619 (Nov. 2018), A178, 13 p.Abundância estelarEstrelas gigantesAglomerados globularesStars: abundancesGalaxy: bulgeGlobular clusters: individual: NGC 6558High-resolution abundance analysis of four red giants in the globular cluster NGC 6558Estrangeiroinfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/openAccessreponame:Repositório Institucional da UFRGSinstname:Universidade Federal do Rio Grande do Sul (UFRGS)instacron:UFRGSTEXT001109427.pdf.txt001109427.pdf.txtExtracted Texttext/plain54628http://www.lume.ufrgs.br/bitstream/10183/203997/2/001109427.pdf.txtcf71a5347bee3a140a8c1c049ae2ec51MD52ORIGINAL001109427.pdfTexto completo (inglês)application/pdf1819779http://www.lume.ufrgs.br/bitstream/10183/203997/1/001109427.pdfbceb1b0bf868b642100824906c8fb5bdMD5110183/2039972023-10-25 03:39:12.87362oai:www.lume.ufrgs.br:10183/203997Repositório de PublicaçõesPUBhttps://lume.ufrgs.br/oai/requestopendoar:2023-10-25T06:39:12Repositório Institucional da UFRGS - Universidade Federal do Rio Grande do Sul (UFRGS)false |
dc.title.pt_BR.fl_str_mv |
High-resolution abundance analysis of four red giants in the globular cluster NGC 6558 |
title |
High-resolution abundance analysis of four red giants in the globular cluster NGC 6558 |
spellingShingle |
High-resolution abundance analysis of four red giants in the globular cluster NGC 6558 Barbuy, Beatriz Abundância estelar Estrelas gigantes Aglomerados globulares Stars: abundances Galaxy: bulge Globular clusters: individual: NGC 6558 |
title_short |
High-resolution abundance analysis of four red giants in the globular cluster NGC 6558 |
title_full |
High-resolution abundance analysis of four red giants in the globular cluster NGC 6558 |
title_fullStr |
High-resolution abundance analysis of four red giants in the globular cluster NGC 6558 |
title_full_unstemmed |
High-resolution abundance analysis of four red giants in the globular cluster NGC 6558 |
title_sort |
High-resolution abundance analysis of four red giants in the globular cluster NGC 6558 |
author |
Barbuy, Beatriz |
author_facet |
Barbuy, Beatriz Muniz, Leone V. Ortolani, Sergio Ernandes, Heitor Dias, Bruno Moreira de Souza Saviane, Ivo Kerber, Leandro de Oliveira Bica, Eduardo Luiz Damiani Pérez Villegas, Maria de Los Angeles Rossi, Luca James Held, Enrico V. |
author_role |
author |
author2 |
Muniz, Leone V. Ortolani, Sergio Ernandes, Heitor Dias, Bruno Moreira de Souza Saviane, Ivo Kerber, Leandro de Oliveira Bica, Eduardo Luiz Damiani Pérez Villegas, Maria de Los Angeles Rossi, Luca James Held, Enrico V. |
author2_role |
author author author author author author author author author author |
dc.contributor.author.fl_str_mv |
Barbuy, Beatriz Muniz, Leone V. Ortolani, Sergio Ernandes, Heitor Dias, Bruno Moreira de Souza Saviane, Ivo Kerber, Leandro de Oliveira Bica, Eduardo Luiz Damiani Pérez Villegas, Maria de Los Angeles Rossi, Luca James Held, Enrico V. |
dc.subject.por.fl_str_mv |
Abundância estelar Estrelas gigantes Aglomerados globulares |
topic |
Abundância estelar Estrelas gigantes Aglomerados globulares Stars: abundances Galaxy: bulge Globular clusters: individual: NGC 6558 |
dc.subject.eng.fl_str_mv |
Stars: abundances Galaxy: bulge Globular clusters: individual: NGC 6558 |
description |
Context. NGC 6558 is a bulge globular cluster with a blue horizontal branch (BHB), combined with a metallicity of [Fe/H] ≈ −1.0. It is similar to HP 1 and NGC 6522, which could be among the oldest objects in the Galaxy. Element abundances in these clusters could reveal the nature of the first supernovae. Aims. We aim to carry out detailed spectroscopic analysis for four red giants of NGC 6558, in order to derive the abundances of the light elements C, N, O, Na, Al, the α-elements Mg, Si, Ca, Ti, and the heavy elements Y, Ba, and Eu. Methods. High-resolution spectra of four stars with FLAMES-UVES at VLT UT2-Kueyen were analysed. Spectroscopic parameter-derivation was based on excitation and ionization equilibrium of Fe I and Fe II. Results. This analysis results in a metallicity of [Fe/H] = − 1.17 ± 0.10 for NGC 6558. We find the expected α-element enhancements in O and Mg with [O/Fe] = +0.40, [Mg/Fe] = +0.33, and low enhancements in Si and Ca. Ti has a moderate enhancement of [Ti/Fe] = +0.22. The r-element Eu appears very enhanced with a mean value of [Eu/Fe] = +0.63. The first peak s-elements Y and Sr are also enhanced, these results have however to be treated with caution, given the uncertainties in the continuum definition; the use of neutral species (Sr I, Y I), instead of the dominant ionized species is another source of uncertainty. Ba appears to have a solar abundance ratio relative to Fe. Conclusions. NGC 6558 shows an abundance pattern that could be typical of the oldest inner bulge globular clusters, together with the pattern in the similar clusters NGC 6522 and HP 1. They show low abundances of the odd-Z elements Na and Al, and of the explosive nucleosynthesis α-elements Si, Ca, and Ti. The hydrostatic burning α-elements O and Mg are normally enhanced as expected in old stars enriched with yields from core-collapse supernovae, and the iron-peak elements Mn, Cu, Zn show low abundances, which is expected for Mn and Cu, but not for Zn. Finally, the cluster trio NGC 6558, NGC 6522, and HP 1 have relatively high abundances of first-peak heavy elements, variable second-peak element Ba, and the r-element Eu is enhanced. The latter is particularly high in NGC 6558. |
publishDate |
2018 |
dc.date.issued.fl_str_mv |
2018 |
dc.date.accessioned.fl_str_mv |
2019-12-28T04:03:15Z |
dc.type.driver.fl_str_mv |
Estrangeiro info:eu-repo/semantics/article |
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info:eu-repo/semantics/publishedVersion |
format |
article |
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publishedVersion |
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http://hdl.handle.net/10183/203997 |
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0004-6361 |
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001109427 |
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0004-6361 001109427 |
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http://hdl.handle.net/10183/203997 |
dc.language.iso.fl_str_mv |
eng |
language |
eng |
dc.relation.ispartof.pt_BR.fl_str_mv |
Astronomy and astrophysics. Les Ulis. Vol. 619 (Nov. 2018), A178, 13 p. |
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openAccess |
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