EDP Sciences
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Volume 387, Number 1, May III 2002
Page(s) 222 - 232
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20020355

A&A 387, 222-232 (2002)
DOI: 10.1051/0004-6361:20020355

UVES Be observations of early-G dwarfs in old clusters

S. Randich1, F. Primas2, L. Pasquini2 and R. Pallavicini3

1  INAF/Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
2  European Southern Observatory Karl Schwarzschild Strasse 2, 85748 Garching bei München, Germany
3  INAF/Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy

(Received 10 October 2001 / Accepted 6 March 2002 )

We have obtained the first beryllium measurements of late F/early G-type stars in the old open cluster  M 67 (4.5 Gyr) and in the intermediate age cluster IC 4651 (1.7 Gyr). One member of the young cluster IC 2391 (~50 Myr) was also observed. Our sample stars have effective temperatures within a range of +30-+380 K from the solar temperature. All our sample stars, including the Sun and the young cluster star have, within the errors, the same Be abundance. This result implies that late F/early G-type stars undergo very little (if any) Be depletion during their main-sequence life-time. Since these stars have undergone some Li depletion, our finding is indicative of shallow mixing, i.e. of a mixing process that can transport surface material deep enough for Li burning to occur, but not deep enough for Be burning. As shown in previous studies, the Li vs. Be diagram is a powerful diagnostic of stellar interiors. In this context, we do not find any evidence of correlated Li and Be depletion; furthermore, a comparison with various models shows that the Be pattern of our sample stars is compatible only with models including gravity waves. This class of models, however, cannot reproduce the Li observations of M 67.

Key words: stars: abundances -- stars: evolution -- open clusters and associations: individual: M 67 -- open clusters and associations: individual: IC 4651

Offprint request: S. Randich, randich@arcetri.astro.it

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© ESO 2002