Issue |
A&A
Volume 439, Number 3, September I 2005
|
|
---|---|---|
Page(s) | 1075 - 1091 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20042396 | |
Published online | 12 August 2005 |
Full computation of massive AGB evolution
II. The role of mass loss and cross-sections
Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monte Porzio Catone, Italy e-mail: [ventura;dantona]@mporzio.astro.it
Received:
19
November
2004
Accepted:
26
April
2005
In the course of a systematic exploration of the uncertainties
associated with the input micro- and macro-physics in the modeling of
the evolution
of intermediate mass stars during their Asymptotic Giant Branch (AGB) phase,
we focus on the role of the nuclear reactions rates and mass loss. We
consider masses
for a metallicity
typical for globular clusters,
, and compare the results
obtained by computing the full
nucleosynthesis with hot bottom burning (HBB), for a network of
30 elements, using either the NACRE or the Cameron & Fowler (CF88)
cross-sections.
The results differ in particular with respect to the 23Na nucleosynthesis (which is more efficient in the NACRE case) and the
magnesium isotopes ratios. For both choices, however, the CNO nucleosynthesis shows that the C+N+O is constant within a factor
of two, in our models
employing a very efficient convection treatment. Different mass loss rates
alter the physical conditions for HBB and the length of the AGB phase,
indirectly changing the chemical yields. These computations show that the
predictive power of our AGB models is undermined by these uncertainties. In
particular, it appears at the moment very difficult to strongly accept
or dismiss that these sources play a key-role in
the pollution of Globular Clusters (GCs), and
that they have been the main stellar site
responsible for the chemical anomalies that
are observed at the surface of giant and turn-off stars of GCs, in the
self-enrichment scenarios.
Key words: stars: evolution / stars: interiors / stars: AGB and post-AGB / stars: abundances
© ESO, 2005
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