Volume 543, July 2012
|Number of page(s)||6|
|Section||Galactic structure, stellar clusters and populations|
|Published online||06 July 2012|
1 INAF – Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
2 Dept. of Physics and Astronomy, Macquarie University, Sydney, NSW, 2109 Australia
3 INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
Received: 26 March 2012
Accepted: 30 May 2012
We studied the distribution of aluminum abundances among red giants in the peculiar globular cluster NGC 1851. Aluminum abundances were derived from the strong doublet Al i 8772–8773 Å measured on intermediate-resolution FLAMES spectra of 50 cluster stars acquired under the Gaia-ESO public survey. We coupled these abundances with previously derived abundances of O, Na, and Mg to fully characterize the interplay of the NeNa and MgAl cycles of H-burning at high temperature in the early stellar generation in NGC 1851. The stars in our sample show well-defined correlations between Al, Na and Si; Al is anticorrelated with O and Mg. The average value of the [Al/Fe] ratio steadily increases from the first generation stars to the second generation populations with intermediate and extremely modified composition. We confirm on a larger database the results recently obtained by us: the pattern of abundances of proton-capture elements implies a moderate production of Al in NGC 1851. We find evidence of a statistically significant positive correlation between Al and Ba abundances in the more metal-rich component of red giants in NGC 1851.
Key words: stars: abundances / stars: atmospheres / stars: Population II / globular clusters: general / globular clusters: individual: NGC 1851
Table 1 is available in electronic form at http://www.aanda.org
© ESO, 2012
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