Publications
of the
MPIfR
Optical & Infrared
Interferometry Group
F. Herwig, D. Schönberner and T.
Blöcker:
Violation of the Core Mass - Luminosity
Relation for AGB models
which experience the third dredge-up
Abstract (poster) for
IAU Symp. 191, Asymptotic Giant Branch Stars, Aug 27th - Sep 1rst,
1998,
Montpellier, France
Abstract.
The third dredge-up phenomenon of thermal pulse AGB stars
is responsible for the enrichment of the stellar envelope with
elements which originate from the nuclear processes within the
shell burning regions. While the observational evidence
for this mechanism is well established today, the stellar evolution
models
usually fail to reproduce the required amount of dredge-up
for core masses of 0.6 Msol < M_H < 0.8 Msol.
We have carried out complete evolutionary calculations of
thermal pulse AGB stellar models which
consider overshoot according to an exponential diffusive algorithm
(Herwig et al. 1997).
The models do show a considerable amount of dredge-up.
In this contribution we investigate the influence of
the dredge-up mechanism on the prediction of the
Core Mass - Luminosity Relation. We show that models
of the above mentioned range of core masses,
wich experience strong dredge-up,
do not follow the classical linear
Core Mass - Luminosity Relation (Herwig 1998).
Although dredge up leads to a substantial reduction
of the core-mass growth after the thermal pulse
the luminosity continues to steadily increase from
pulse to pulse.
References:
Herwig, F., 1998, PhD Thesis, Universität Kiel
Herwig, F., Blöcker, T., Schönberner, D., El Eid, M.,
1997, A&A 324, L81