Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 434, Issue 4, Pages 3542-3565Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stt1276
Keywords
stars: abundances; Galaxy: abundances; globular clusters: individual: NGC 6752
Categories
Funding
- Australian Research Council [DP0984924, FL110100012, DP120100475, DP120100991, DE120102940]
- FAPESP [2010/17510-3, 2012/24392-2, 2008/58406-4]
- CNPq (Bolsa de Produtividade)
- Danish National Research Foundation
- ASTERISK project
- European Research Council [267864]
- Carnegie Institution for Science through the Barbara McClintock Fellowship
- Australian Research Council [DE120102940] Funding Source: Australian Research Council
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We report on a strictly differential line-by-line analysis of high-quality UVES spectra of bright giants in the metal-poor globular cluster NGC 6752. We achieved high precision differential chemical abundance measurements for Fe, Na, Si, Ca, Ti, Cr, Ni, Zn, Y, Zr, Ba, La, Ce, Pr, Nd, Sm, Eu and Dy with uncertainties as low as similar to 0.01 dex (similar to 2 per cent). We obtained the following main results. (1) The observed abundance dispersions are a factor of similar to 2 larger than the average measurement uncertainty. (2) There are positive correlations, of high statistical significance, between all elements and Na. (3) For any pair of elements, there are positive correlations of high statistical significance, although the amplitudes of the abundance variations are small. Removing abundance trends with effective temperature and/or using a different pair of reference stars does not alter these results. These abundance variations and correlations may reflect a combination of (a) He abundance variations and (b) inhomogeneous chemical evolution in the pre- or protocluster environment. Regarding the former, the current constraints on delta Y from photometry likely preclude He as being the sole explanation. Regarding the latter, the nucleosynthetic source(s) must have synthesized Na, alpha, Fe-peak and neutron-capture elements and in constant amounts for species heavier than Si; no individual object can achieve such nucleosynthesis. We speculate that other, if not all, globular clusters may exhibit comparable abundance variations and correlations to NGC 6752 if subjected to a similarly precise analysis.
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