EDP Sciences
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Volume 439, Number 1, August III 2005
Page(s) 227 - 235
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:20041805

A&A 439, 227-235 (2005)
DOI: 10.1051/0004-6361:20041805

On the nature of lithium-rich giant stars

Constraints from beryllium abundances
C. H. F. Melo1, P. de Laverny2, N. C. Santos3, 4, G. Israelian5, S. Randich6, J. D. do Nascimento Jr7 and J. R. De Medeiros7

1  European Southern Observatory, Casilla 19001, Santiago 19, Chile
    e-mail: cmelo@eso.org
2  Observatoire de la Côte d'Azur, Département Cassiopée, UMR 6202, BP 4229, 06304 Nice, France
3  Centro de Astronomia e Astrofíca da Universidade de Lisboa, Observatório Astronómico de Lisboa, Tapada da Ajuda, 1349-018 Lisboa, Portugal
4  Observatoire de Genève, 51 ch. des Maillettes, 1290 Sauverny, Switzerland
5  Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
6  INAF/Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
7  Departamento de Física, Universidade Federal do Rio Grande do Norte, 59072-970 Natal, RN., Brazil

(Received 5 August 2004 / Accepted 29 March 2005 )

We have derived beryllium abundances for 7 Li-rich giant ( $A(\rm Li) > 1.5$) stars and 10 other Li-normal giants with the aim of investigating the origin of the lithium in the Li-rich giants. In particular, we test the predictions of the engulfment scenario proposed by Siess & Livio (1999, MNRAS, 308, 1133), where the engulfment of a brown dwarf or one or more giant planets would lead to simultaneous enrichment of 7Li and 9Be. We show that regardless of their nature, none of the stars studied in this paper were found to have detectable beryllium. Using simple dilution arguments we show that engulfment of an external object as the sole source of Li enrichment is ruled out by the Li and Be abundance data. The present results favor the idea that Li has been produced in the interior of the stars by a Cameron-Fowler process and brought up to the surface by an extra mixing mechanism.

Key words: stars: abundances -- stars: interiors -- stars: late-type

SIMBAD Objects

© ESO 2005