Publications
of the
MPIfR
Optical & Infrared
Interferometry Group
T. Driebe, T. Blöcker, F. Herwig and D.
Schönberner:
Diffusive Overshooting in Hot Bottom Burning
AGB Models
Astronomische Gesellschaft Meeting Abstracts
(AGM 14, P30)
Poster presented at the Annual Scientific Meeting of the Astronomische
Gesellschaft
at Heidelberg, September 14-19, 1998
Abstract.
The concept of diffusive overshooting based on hydrodynamical
simulations of
convection zones (Freytag et al., A&A 313, 497, 1996) has recently
been
introduced to AGB models. For a 3 Msol AGB model sequence,
Herwig et al. (1997, A&A 324, L81) found with this prescription of
additional slow mixing substantial dredge up, i.e. the production of
carbon stars for relatively low masses. This scheme leads as well
to the formation of a C13 pocket which is required to drive the
s-process
in these stars.
In this study we focus on the influence of exponential diffusive
overshoot
on more massive AGB models which suffer from hot bottom burning (HBB),
i.e. the penetration of the envelope convection into the
hydrogen-burning shell. It is well known that HBB leads to the
break-down
of the core-mass luminosity relation, to the formation of Li-rich AGB
stars
and to the, at least temporary, prevention of the carbon-star
stage due to CN cycling of the by dredge-up episodes
carbon-enriched envelopes. However, the efficiency of
HBB depends considerably on the treatment of convection.
We calculated model sequences for initial masses of 3 to 6 Msol from
the
main sequence through the AGB considering diffusive overshoot in all
evolutionary stages and convection zones. We discuss onset and
strength of HBB in these models and differences to standard
calculations
without overshoot.
You can get this publication ...