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
Abstract (poster) for
IAU Symp. 191, Asymptotic Giant Branch Stars, Aug 27th - Sep 1rst,
1998,
Montpellier, France
Abstract.
The concept of diffusive overshooting based on hydrodynamical
simulations of convection zones (Freytag et al. 1996)
has already been successfully introduced to AGB models by Herwig et al.
(1997).
For a 3 Msol AGB model sequence,
Herwig et al. (1997) found with this prescription of additional
slow mixing dredge up, i.e. the production of carbon stars of
relatively low
masses, as well as the formation of a C13 pocket to drive the s-process
in these stars.
In this study we investigate the influence of the exponential
diffusive overshoot scheme on more massive AGB models which suffer
from hot bottom burning (HBB). It is well known that HBB leads to the
break-down of the core-mass luminosity relation and to the formation of
Li-rich AGB stars.
Additionally, it may prevent, at least temporarily,
the carbon-star stage due to CN cycling of the enriched envelope
matter.
These important consequences of HBB depend
considerably on the treatment of convection (and mass loss).
Consequently, the efficiency of HBB and its competition with
dredge-up episodes depend also on the aforementioned additional
slow mixing processes
which obviously successfully operate at and below the H/He interface.
References:
Freytag B., Ludwig H.-G., Steffen M. 1996, A&A 313, 497
Herwig, F., Blöcker, T., Schönberner, D., El Eid, M.,
1997, A&A 324, L81
You can get this abstract ...