High-resolution abundance analysis of red giants in the globular cluster NGC 6522
Autor(a) principal: | |
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Data de Publicação: | 2014 |
Outros Autores: | , , , , , , , , , , , , |
Tipo de documento: | Artigo |
Idioma: | eng |
Título da fonte: | Repositório Institucional da UFRGS |
Texto Completo: | http://hdl.handle.net/10183/126968 |
Resumo: | Context. The [Sr/Ba] and [Y/Ba] scatter observed in some galactic halo stars that are very metal-poor and in a few individual stars of the oldest known Milky Way globular cluster NGC 6522 have been interpreted as evidence of early enrichment by massive fastrotating stars (spinstars). Because NGC 6522 is a bulge globular cluster, the suggestion was that not only the very-metal poor halo stars, but also bulge stars at [Fe/H] ∼−1 could be used as probes of the stellar nucleosynthesis signatures from the earlier generations of massive stars, but at much higher metallicity. For the bulge the suggestions were based on early spectra available for stars in NGC 6522, with a medium resolution of R ∼ 22 000 and a moderate signal-to-noise ratio. Aims. The main purpose of this study is to re-analyse the NGC 6522 stars reported previously by using new high-resolution (R ∼ 45 000) and high signal-to-noise spectra (S /N > 100).We aim at re-deriving their stellar parameters and elemental ratios, in particular the abundances of the neutron-capture s-process-dominated elements such as Sr, Y, Zr, La, and Ba, and of the r-element Eu. Methods. High-resolution spectra of four giants belonging to the bulge globular cluster NGC 6522 were obtained at the 8m VLT UT2-Kueyen telescope with the UVES spectrograph in FLAMES-UVES configuration. The spectroscopic parameters were derived based on the excitation and ionization equilibrium of Fe i and Fe ii. Results. Our analysis confirms a metallicity [Fe/H] = −0.95 ± 0.15 for NGC 6522 and the overabundance of the studied stars in Eu (with +0.2 < [Eu/Fe] < +0.4) and alpha-elements O and Mg. The neutron-capture s-element-dominated Sr, Y, Zr, Ba, and La now show less pronounced variations from star to star. Enhancements are in the range 0.0 < [Sr/Fe] < +0.4, +0.23 < [Y/Fe] < +0.43, 0.0 < [Zr/Fe] < +0.4, 0.0 < [La/Fe] < +0.35, and 0.05 < [Ba/Fe] < +0.55. Conclusions. The very high overabundances of [Y/Fe] previously reported for the four studied stars is not confirmed with the new high-quality spectra. The moderate enhancement in [Sr/Fe] previously reported for one of the re-studied stars is confirmed, but the strong enhancements of this ratio for the other two stars are not confirmed. Despite the moderate enhancements found for the neutroncapture s-element-dominated species, none of the four stars studied here show positive values for all [Sr/Ba], [Y/Ba] and [Zr/Ba] ratios. The re-studied stars are now compatible not only with the interpretation that the s-process enhancements in these very old stars are due to spinstars, but also with alternative models such as mass transfer from s-process-rich AGB stars. Note, however, that when our results are interpreted in the context of more extended datasets from the literature, the spinstar scenario still seems to be favoured. |
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Barbuy, BeatrizChiappini, C.C.M.Cantelli, Elvis William CarvalhoDepagne, ÉricPignatari, MarcoHirschi, RaphaelCescutti, GabrieleOrtolani, SergioHill, VanessaZoccali, ManuelaMinniti, DanteTrevisan, MarinaBica, Eduardo Luiz DamianiGómez, Ana2015-09-18T01:58:23Z20140004-6361http://hdl.handle.net/10183/126968000972460Context. The [Sr/Ba] and [Y/Ba] scatter observed in some galactic halo stars that are very metal-poor and in a few individual stars of the oldest known Milky Way globular cluster NGC 6522 have been interpreted as evidence of early enrichment by massive fastrotating stars (spinstars). Because NGC 6522 is a bulge globular cluster, the suggestion was that not only the very-metal poor halo stars, but also bulge stars at [Fe/H] ∼−1 could be used as probes of the stellar nucleosynthesis signatures from the earlier generations of massive stars, but at much higher metallicity. For the bulge the suggestions were based on early spectra available for stars in NGC 6522, with a medium resolution of R ∼ 22 000 and a moderate signal-to-noise ratio. Aims. The main purpose of this study is to re-analyse the NGC 6522 stars reported previously by using new high-resolution (R ∼ 45 000) and high signal-to-noise spectra (S /N > 100).We aim at re-deriving their stellar parameters and elemental ratios, in particular the abundances of the neutron-capture s-process-dominated elements such as Sr, Y, Zr, La, and Ba, and of the r-element Eu. Methods. High-resolution spectra of four giants belonging to the bulge globular cluster NGC 6522 were obtained at the 8m VLT UT2-Kueyen telescope with the UVES spectrograph in FLAMES-UVES configuration. The spectroscopic parameters were derived based on the excitation and ionization equilibrium of Fe i and Fe ii. Results. Our analysis confirms a metallicity [Fe/H] = −0.95 ± 0.15 for NGC 6522 and the overabundance of the studied stars in Eu (with +0.2 < [Eu/Fe] < +0.4) and alpha-elements O and Mg. The neutron-capture s-element-dominated Sr, Y, Zr, Ba, and La now show less pronounced variations from star to star. Enhancements are in the range 0.0 < [Sr/Fe] < +0.4, +0.23 < [Y/Fe] < +0.43, 0.0 < [Zr/Fe] < +0.4, 0.0 < [La/Fe] < +0.35, and 0.05 < [Ba/Fe] < +0.55. Conclusions. The very high overabundances of [Y/Fe] previously reported for the four studied stars is not confirmed with the new high-quality spectra. The moderate enhancement in [Sr/Fe] previously reported for one of the re-studied stars is confirmed, but the strong enhancements of this ratio for the other two stars are not confirmed. Despite the moderate enhancements found for the neutroncapture s-element-dominated species, none of the four stars studied here show positive values for all [Sr/Ba], [Y/Ba] and [Zr/Ba] ratios. The re-studied stars are now compatible not only with the interpretation that the s-process enhancements in these very old stars are due to spinstars, but also with alternative models such as mass transfer from s-process-rich AGB stars. Note, however, that when our results are interpreted in the context of more extended datasets from the literature, the spinstar scenario still seems to be favoured.application/pdfengAstronomy and astrophysics. Les Ulis. Vol. 570 (Oct. 2014), A76, 21 p.Estrelas gigantesAglomerados estelares globularesComposicao estelarMassa estelarRotacao estelarEspectros estelaresIonizaçãoTransferência de massaStars: abundancesStars: atmospheresGalaxy: bulgeGlobular clusters: individual: NGC 6522High-resolution abundance analysis of red giants in the globular cluster NGC 6522Estrangeiroinfo: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:UFRGSORIGINAL000972460.pdf000972460.pdfTexto completo (inglês)application/pdf1151529http://www.lume.ufrgs.br/bitstream/10183/126968/1/000972460.pdfbd4d7cd0b2e218cab2095776b5e1182eMD51TEXT000972460.pdf.txt000972460.pdf.txtExtracted Texttext/plain89589http://www.lume.ufrgs.br/bitstream/10183/126968/2/000972460.pdf.txt2ac8c81d858bac4959fe016fb6d0c051MD52THUMBNAIL000972460.pdf.jpg000972460.pdf.jpgGenerated Thumbnailimage/jpeg2041http://www.lume.ufrgs.br/bitstream/10183/126968/3/000972460.pdf.jpg4d817577f1dff9065e0e34e8c587e1caMD5310183/1269682023-08-11 03:52:24.237448oai:www.lume.ufrgs.br:10183/126968Repositório de PublicaçõesPUBhttps://lume.ufrgs.br/oai/requestopendoar:2023-08-11T06:52:24Repositório Institucional da UFRGS - Universidade Federal do Rio Grande do Sul (UFRGS)false |
dc.title.pt_BR.fl_str_mv |
High-resolution abundance analysis of red giants in the globular cluster NGC 6522 |
title |
High-resolution abundance analysis of red giants in the globular cluster NGC 6522 |
spellingShingle |
High-resolution abundance analysis of red giants in the globular cluster NGC 6522 Barbuy, Beatriz Estrelas gigantes Aglomerados estelares globulares Composicao estelar Massa estelar Rotacao estelar Espectros estelares Ionização Transferência de massa Stars: abundances Stars: atmospheres Galaxy: bulge Globular clusters: individual: NGC 6522 |
title_short |
High-resolution abundance analysis of red giants in the globular cluster NGC 6522 |
title_full |
High-resolution abundance analysis of red giants in the globular cluster NGC 6522 |
title_fullStr |
High-resolution abundance analysis of red giants in the globular cluster NGC 6522 |
title_full_unstemmed |
High-resolution abundance analysis of red giants in the globular cluster NGC 6522 |
title_sort |
High-resolution abundance analysis of red giants in the globular cluster NGC 6522 |
author |
Barbuy, Beatriz |
author_facet |
Barbuy, Beatriz Chiappini, C.C.M. Cantelli, Elvis William Carvalho Depagne, Éric Pignatari, Marco Hirschi, Raphael Cescutti, Gabriele Ortolani, Sergio Hill, Vanessa Zoccali, Manuela Minniti, Dante Trevisan, Marina Bica, Eduardo Luiz Damiani Gómez, Ana |
author_role |
author |
author2 |
Chiappini, C.C.M. Cantelli, Elvis William Carvalho Depagne, Éric Pignatari, Marco Hirschi, Raphael Cescutti, Gabriele Ortolani, Sergio Hill, Vanessa Zoccali, Manuela Minniti, Dante Trevisan, Marina Bica, Eduardo Luiz Damiani Gómez, Ana |
author2_role |
author author author author author author author author author author author author author |
dc.contributor.author.fl_str_mv |
Barbuy, Beatriz Chiappini, C.C.M. Cantelli, Elvis William Carvalho Depagne, Éric Pignatari, Marco Hirschi, Raphael Cescutti, Gabriele Ortolani, Sergio Hill, Vanessa Zoccali, Manuela Minniti, Dante Trevisan, Marina Bica, Eduardo Luiz Damiani Gómez, Ana |
dc.subject.por.fl_str_mv |
Estrelas gigantes Aglomerados estelares globulares Composicao estelar Massa estelar Rotacao estelar Espectros estelares Ionização Transferência de massa |
topic |
Estrelas gigantes Aglomerados estelares globulares Composicao estelar Massa estelar Rotacao estelar Espectros estelares Ionização Transferência de massa Stars: abundances Stars: atmospheres Galaxy: bulge Globular clusters: individual: NGC 6522 |
dc.subject.eng.fl_str_mv |
Stars: abundances Stars: atmospheres Galaxy: bulge Globular clusters: individual: NGC 6522 |
description |
Context. The [Sr/Ba] and [Y/Ba] scatter observed in some galactic halo stars that are very metal-poor and in a few individual stars of the oldest known Milky Way globular cluster NGC 6522 have been interpreted as evidence of early enrichment by massive fastrotating stars (spinstars). Because NGC 6522 is a bulge globular cluster, the suggestion was that not only the very-metal poor halo stars, but also bulge stars at [Fe/H] ∼−1 could be used as probes of the stellar nucleosynthesis signatures from the earlier generations of massive stars, but at much higher metallicity. For the bulge the suggestions were based on early spectra available for stars in NGC 6522, with a medium resolution of R ∼ 22 000 and a moderate signal-to-noise ratio. Aims. The main purpose of this study is to re-analyse the NGC 6522 stars reported previously by using new high-resolution (R ∼ 45 000) and high signal-to-noise spectra (S /N > 100).We aim at re-deriving their stellar parameters and elemental ratios, in particular the abundances of the neutron-capture s-process-dominated elements such as Sr, Y, Zr, La, and Ba, and of the r-element Eu. Methods. High-resolution spectra of four giants belonging to the bulge globular cluster NGC 6522 were obtained at the 8m VLT UT2-Kueyen telescope with the UVES spectrograph in FLAMES-UVES configuration. The spectroscopic parameters were derived based on the excitation and ionization equilibrium of Fe i and Fe ii. Results. Our analysis confirms a metallicity [Fe/H] = −0.95 ± 0.15 for NGC 6522 and the overabundance of the studied stars in Eu (with +0.2 < [Eu/Fe] < +0.4) and alpha-elements O and Mg. The neutron-capture s-element-dominated Sr, Y, Zr, Ba, and La now show less pronounced variations from star to star. Enhancements are in the range 0.0 < [Sr/Fe] < +0.4, +0.23 < [Y/Fe] < +0.43, 0.0 < [Zr/Fe] < +0.4, 0.0 < [La/Fe] < +0.35, and 0.05 < [Ba/Fe] < +0.55. Conclusions. The very high overabundances of [Y/Fe] previously reported for the four studied stars is not confirmed with the new high-quality spectra. The moderate enhancement in [Sr/Fe] previously reported for one of the re-studied stars is confirmed, but the strong enhancements of this ratio for the other two stars are not confirmed. Despite the moderate enhancements found for the neutroncapture s-element-dominated species, none of the four stars studied here show positive values for all [Sr/Ba], [Y/Ba] and [Zr/Ba] ratios. The re-studied stars are now compatible not only with the interpretation that the s-process enhancements in these very old stars are due to spinstars, but also with alternative models such as mass transfer from s-process-rich AGB stars. Note, however, that when our results are interpreted in the context of more extended datasets from the literature, the spinstar scenario still seems to be favoured. |
publishDate |
2014 |
dc.date.issued.fl_str_mv |
2014 |
dc.date.accessioned.fl_str_mv |
2015-09-18T01:58:23Z |
dc.type.driver.fl_str_mv |
Estrangeiro info:eu-repo/semantics/article |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
format |
article |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
http://hdl.handle.net/10183/126968 |
dc.identifier.issn.pt_BR.fl_str_mv |
0004-6361 |
dc.identifier.nrb.pt_BR.fl_str_mv |
000972460 |
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0004-6361 000972460 |
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http://hdl.handle.net/10183/126968 |
dc.language.iso.fl_str_mv |
eng |
language |
eng |
dc.relation.ispartof.pt_BR.fl_str_mv |
Astronomy and astrophysics. Les Ulis. Vol. 570 (Oct. 2014), A76, 21 p. |
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eu_rights_str_mv |
openAccess |
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