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.
Carretta, E., D'Orazi, V., Gratton, R.g., Lucatello, S. (2012). Aluminum abundances of multiple stellar generations in the globular cluster NGC 1851. ASTRONOMY & ASTROPHYSICS, 543 [10.1051/0004-6361/201219277].
Aluminum abundances of multiple stellar generations in the globular cluster NGC 1851
D'Orazi, V.;
2012-01-01
Abstract
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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.