NOAO >   Observing Info >   Approved Programs >   2010A-0357

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Proposal Information for 2010A-0357


PI: Roberto De Propris, Cerro Tololo Inter-American Observatory, rdepropris@ctio.noao.edu
Address: Casilla 603, La Serena, Chile

CoI: Simon Schuler, KPNO
CoI: Anna Frebel, Center for Astrophysics
CoI: Francesca D'Antona, Osservatorio Astronomico di Roma
CoI: Paolo Ventura, Osservatorio Astronomico di Roma
CoI: Giampaolo Piotto, Universita' di Padova
CoI: Antonino Milone, Universita' di Padova

Title: The triple sequence of NGC 2808: exploring the stellar abundances

Abstract: NGC 2808 is one of the globular clusters containing multiple stellar populations in our Galaxy. The cluster color-magnitude diagram contains two extra sequences blueward of the main cluster ridge-line. Stars on these sequences appear to be enhanced in Helium up to Y=0.40. The origin of these stars is still mysterious although they are believed to be produced from the ejecta of massive AGB stars. We propose here to take echelle spectra for several stars (~ 100) on each of the three sequences and build a high signal-to-noise stacked spectrum to derive the detailed chemical abundances of the average `star' on each of the three NGC 2808 sequences. We are particularly interested in the elements known to be involved in anticorrelations on the giant branch (O, Na, Mg, Al) and the r- and s-process element abundances (Ba, Eu), as well as Fe and Li. The relative enrichment in these elements across the three sequences will point to the nature of the polluting populations.


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