Bibcode
García-Hernández, D. A.; García-Lario, P.; Plez, B.; Manchado, A.; D'Antona, F.
Referencia bibliográfica
Planetary Nebulae in our Galaxy and Beyond, Proceedings of the International Astronomical Union, Symposium #234. Edited by Michael J. Barlow and Roberto H. Méndez. Cambridge: Cambridge University Press, 2006., pp.87-90
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2006
Número de citas
3
Número de citas referidas
3
Descripción
We present the main results derived from a chemical abundance analysis
carried out on a large sample of massive galactic O-rich AGB stars (M
> 3-4 M_&sun;). Combining these results with previous studies made
on a similar sample of luminous AGB stars belonging to the Magellanic
Clouds we provide strong observational evidences that metallicity
effects are playing a more important role than generally assumed in
chemical evolution models. This concerns not only the onset of the
so-called "hot bottom burning", the efficiency of the third dredge-up
and the s-process nucleosynthesis as derived from our optical
observations, but also the dust production efficiency and the chemical
properties of the dust grains in the shell, as inferred from the
available infrared data. We find Li overabundances in the galactic stars
studied, indicating that they are actually "hot bottom burning" AGB
stars. Similar Li overabundances are also observed in the most luminous
Magellanic Cloud AGB stars. However, the AGB stars in our galactic
sample are not enriched in Zr, in contrast to what is observed in the
Magellanic Clouds. In addition, many stars in the galactic sample appear
heavily obscured in the optical, suggesting a much more efficient dust
production and/or stronger mass loss rates which eventually can be
translated into shorter AGB lifetimes.