Issue |
A&A
Volume 442, Number 2, November I 2005
|
|
---|---|---|
Page(s) | 615 - 627 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20053482 | |
Published online | 07 October 2005 |
Time scales of Li evolution: a homogeneous analysis of open clusters from ZAMS to late-MS
1
INAF/Osservatorio Astronomico di Bologna, Via C. Ranzani 1, 40127 Bologna, Italy e-mail: paola.sestito@bo.astro.it
2
INAF/Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
Received:
20
May
2005
Accepted:
19
July
2005
We have performed a new and homogeneous analysis of all the Li
data available in the literature
for main sequence stars (spectral-types
from late F to K) in open clusters.
In the present paper we focus on a detailed investigation
of MS Li depletion and its time scales for stars in the 6350-5500 K
effective temperature range.
For the first time, we were able to constrain the age at which
non-standard mixing processes, driving MS Li depletion, appear.
We have also shown that MS Li depletion is not a continuous
process and cannot be simply described by a law.
We confirm that depletion becomes ineffective beyond an age of 1-2 Gyr for the
majority of the stars, leading to a Li plateau at old ages.
We compared the empirical scenario of Li as a function of age
with the predictions of three non-standard models. We found that
models including only gravity waves as main mixing process
are not able to fit the Li vs. age pattern
and thus this kind of mixing
can be excluded as the predominant mechanism responsible
for Li depletion. On the other hand, models including slow mixing
induced by rotation and
angular momentum loss, and in particular those including
also diffusive processes not related to rotation,
can explain to some extent the empirical evidence.
However, none of the currently proposed models can fit the plateau
at old ages.
Key words: stars: abundances / stars: evolution / open clusters and associations: general
© ESO, 2005
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