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The chemical composition of red giants in 47 Tucanae II. Magnesium isotopes and pollution scenarios

Thygesen, A. O. and Sbordone, L. and Ludwig, H.-G. and Ventura, P. and Yong, D. and Collet, R. and Christlieb, N. and Melendez, J. and Zaggia, S. (2016) The chemical composition of red giants in 47 Tucanae II. Magnesium isotopes and pollution scenarios. Astronomy and Astrophysics, 588 . Art. No. A66. ISSN 0004-6361.

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Context. The phenomenon of multiple populations in globular clusters is still far from understood, with several proposed mechanisms to explain the observed behaviour. The study of elemental and isotopic abundance patterns are crucial for investigating the differences among candidate pollution mechanisms. Aims. We derive magnesium isotopic ratios for 13 stars in the globular cluster 47 Tucanae (NGC 104) to provide new, detailed information about the nucleosynthesis that has occurred within the cluster. For the first time, the impact of 3D model stellar atmospheres on the derived Mg isotopic ratios is investigated. Methods. Using both tailored 1D atmospheric models and 3D hydrodynamical models, we derive magnesium isotopic ratios from four features of MgH near 5135 Å in 13 giants near the tip of the red giant branch, using high signal-to-noise, high-resolution spectra. Results. We derive the magnesium isotopic ratios for all stars and find no significant offset of the isotopic distribution between the pristine and the polluted populations. Furthermore, we do not detect any statistically significant differences in the spread in the Mg isotopes in either population. No trends were found between the Mg isotopes and [Al/Fe]. The inclusion of 3D atmospheres has a significant impact on the derived ^(25)Mg/^(24)Mg ratio, increasing it by a factor of up to 2.5, compared to 1D. The ^(26)Mg/^(24)Mg ratio, on the other hand, essentially remains unchanged. Conclusions. We confirm the results seen from other globular clusters, where no strong variation in the isotopic ratios is observed between stellar populations, for observed ranges in [Al/Fe]. We see no evidence for any significant activation of the Mg-Al burning chain. The use of 3D atmospheres causes an increase of a factor of up to 2.5 in the fraction of 25Mg, resolving part of the discrepancy between the observed isotopic fraction and the predictions from pollution models.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Thygesen, A. O.0000-0002-4912-1183
Christlieb, N.0000-0002-4043-2727
Zaggia, S.0000-0001-6081-379X
Additional Information:© 2016 ESO. Received 31 May 2015. Accepted 25 January 2016. The authors would like to thank the anonymous referee for their useful comments which helped improve the manuscript. A.O.T., L.S., H.G.L. and N.C. acknowledges support from Sonderforschungsbereich SFB 881 “The Milky Way System” (subprojects A4 and A5) of the German Research Foundation (DFG). LS acknowledges the support by Chile’s Ministry of Economy, Development, and Tourism’s Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. D.Y. was supported through an Australian Research Council Future Fellowship (FT140100554). R.C. acknowledges support from a DECRA grant from the Australian Research Council (project DE120102940). This work has made use of the VALD database, operated at Uppsala University, the Institute of Astronomy RAS in Moscow, and the University of Vienna. This research took advantage of the SIMBAD and VIZIER databases at the CDS, Strasbourg (France), and NASA’s Astrophysics Data System Bibliographic Services.
Funding AgencyGrant Number
Deutsche Forschungsgemeinschaft (DFG)SFB 881
Iniciativa Científica Milenio del Ministerio de Economía, Fomento y TurismoIC120009
Australian Research CouncilFT140100554
Australian Research CouncilDE120102940
Subject Keywords:stars: abundances, techniques: spectroscopic, methods: observational, globular clusters: individual: 47 Tucanae
Record Number:CaltechAUTHORS:20160520-091633470
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Official Citation:The chemical composition of red giants in 47 Tucanae - II. Magnesium isotopes and pollution scenarios A. O. Thygesen, L. Sbordone, H.-G. Ludwig, P. Ventura, D. Yong, R. Collet, N. Christlieb, J. Melendez and S. Zaggia A&A, 588 (2016) A66 DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:67199
Deposited By: Ruth Sustaita
Deposited On:20 May 2016 17:27
Last Modified:09 Mar 2020 13:19

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