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Beryllium abundance in lithium-rich giants *
B.V. Castilho 1,
F. Spite 2,
B. Barbuy 1,
M. Spite 2,
J.R. De Medeiros 3 and
J. Gregorio-Hetem 1
Received 26 November 1998 / Accepted 2 February 1999
About 2 of the Population I red giants show lithium abundances significantly larger than expected by dilution due to mixing by classical convection and, in some of them, the lithium abundance reaches values similar to (and even larger than) the Pop I value (meteoritic, open clusters etc.) around logN(Li) = 3.3. The classical convection predicts also a (smaller) dilution of beryllium and (an even smaller one) of boron.
Two main interpretations of the Li-rich giants are possible:
In the first interpretation, Be (more robust than Li) is a fortiori preserved, in the second one, a mixing deeper than the classical one should dilute Be more than the classical Be dilution.
We have observed the Be II
3130.420 and 3131.066 Å lines in two Li-rich giants and three
reference stars: one Li-poor giant and
Cen A and B. The observations were
carried out at the ESO 3.6m telescope using the CASPEC spectrograph.
By comparing the observed spectra with spectrum synthesis calculations
we show that for the three giant stars the Be abundance is low,
suggesting that, in these giants, Be is very depleted
from the initial Pop I value
(logN(Be)1.4). This result implies
that the original Li in these stars must have been almost completely
destroyed, and that the high Li abundances in the Li-rich red giants
is most probably due to Li production in these stars.
Key words: nuclear reactions, nucleosynthesis, abundances stars: abundances stars: late-type
Send offprint requests to: B.V. Castilho
Online publication: April 12, 1999