AGB evolution with overshoot: hot bottom burning and dredge up

• Main Authors: Bloecker, T, Herwig, F, Driebe, T
• Format: Journal Article
• Language: English
• Published: 24-02-2000
• Subjects: Physics - Astrophysics of Galaxies; Physics - Cosmology and Nongalactic Astrophysics; Physics - Earth and Planetary Astrophysics; Physics - High Energy Astrophysical Phenomena; Physics - Instrumentation and Methods for Astrophysics; Physics - Solar and Stellar Astrophysics
• DOI: 10.48550/arxiv.astro-ph/0002455

We calculated models of massive AGB stars with a self-consistent coupling of
time-dependent mixing and nuclear burning for 30 isotopes and 74 reactions.
Overshoot with an exponentially declining velocity field was considered and
applied during all stages of evolution and in all convective regions. Very
efficient 3rd dredge-up was found even overcompensating the growth of the
hydrogen-exhausted core after a few thermal pulses. Hot bottom burning occurs
for M>4Msol within the sequences with overshoot. Carbon star formation in these
more massive AGB stars is delayed or even prevented by hot bottom burning
despite the very efficient dredge-up. With the simultaneous treatment of mixing
and burning the formation of Li-rich AGB stars due to the Cameron-Fowler
mechanism was followed. For a 6Msol model the maximum Li abundance was found to
be epsilon(Li7)=4.4.