Publications
of the
MPIfR
Optical & Infrared
Interferometry Group
F. Herwig, T. Blöcker and T .Driebe:
TP-AGB evolution with overshoot for low-mass
stars as a function of metallicity
in
The
Changes in Abundances in Asymptotic Giant Branch Stars,
Mem. Soc. Astron. Ital. 71, 745-752 (2000)
Abstract.
We give a brief review on the properties of asymptotic giant branch
models with overshoot. Then we describe new model calculations with
overshoot. Initial masses are ranging from 1 to 3Msol and
metallicities are Z=0.02, 0.01 and 0.001. Third dredge-up occurs
efficiently
for low masses and carbon stars are formed, with some at
core masses as low as 0.58Msol. After the thermal pulse at which stars
become
C-rich the luminosities are in the range of the observed C-star
luminosity
function during the whole interpulse phase and for all C-star
models. The dredge-up evolution depends mainly on the core mass at
the first thermal pulse and on the metallicity. The Z=0.001 models of
the 2 and
3Msol sequence become C-rich almost instantaneously after the onset of
the
first thermal pulses. For the 2Msol case the C/O ratio initially
exceeds 4.
During following dredge-up episodes the C/O ratio decreases.
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