Bibcode
van Raai, M. A.; Lugaro, M.; Karakas, A. I.; García-Hernández, D. A.
Referencia bibliográfica
IXTH TORINO WORKSHOP ON EVOLUTION AND NUCLEOSYNTHESIS IN AGB STARS AND THE IIND PERUGIA WORKSHOP ON NUCLEAR ASTROPHYSICS. AIP Conference Proceedings, Volume 1001, pp. 146-153 (2008).
Fecha de publicación:
4
2008
Número de citas
6
Número de citas referidas
5
Descripción
A recent survey of a large sample of massive Galactic asymptotic giant
branch (AGB) stars shows that significant overabundances of rubidium (up
to 100 times solar), but merely solar zirconium, are present in these
stars. These observations can set constraints on our theoretical notion
of the slow neutron capture process (the s process) in AGB stars, as
well as on the rates of the neutron capture reactions involved in the
production of Rb and Zr. We use the Monash nucleosynthesis code with a
recently extended network to try to reproduce these observations. We
present results for AGB stars of masses 5, 6, and 6.5 Msolar and solar
metallicity. We also show results for different available choices of the
neutron capture rates, as well as for the possible inclusion of a
partial mixing zone (PMZ), leading to the activation of the
13C neutron source. We find increasing Rb overabundances with
increasing stellar mass, as observed, but we are far from matching the
highest observed Rb enhancements. Inclusion of a PMZ increases the Rb
abundance, but also produces an overabundance of Zr, contrary to what is
observed. Only if the third dredge up efficiency remains as high as
before the onset of the superwind phase during the final few pulses of a
massive AGB star, can we match the highest [Rb/Fe] ratios observed by
García-Hernández et al. [l]. A better understanding of the
third dredge up efficiency with decreasing envelope mass for massive AGB
stars is essential for further investigation of this issue.