Publications
of the
MPIfR
Optical & Infrared
Interferometry Group
A. Wachter, K.-P. Schröder, J.M.
Winters, T.U. Arndt, and E. Sedlmayr:
An improved mass-loss description for
dust-driven superwinds
and tip-AGB evolution models
Astronomy & Astrophysics, v.384, p.452-459
(2002)
Abstract.
We derive an improved description of dust-driven stellar mass-loss for
the cool winds of carbon-rich tip-AGB stars. We use pulsating wind
models in which the mass loss is driven by radiation pressure on dust
grains, for C-rich chemistry. From a larger set of these models,
selected for representative dynamical (pulsational velocity amplitude
$\Delta v$, period P) and chemical (the C/O abundance ratio) input
parameters, an improved approximative mass-loss formula has been
derived which depends only on the stellar parameters (effective
temperature Teff, luminosity L and mass M). Due to the
detailed consideration of the chemistry and the physics of the dust
nucleation and growth processes, there is a particularly strong
dependence of the mass-loss rate Mdot (in Mo/yr) on Teff:
log Mdot = 8.86 - 1.95 log M/ Mo - 6.81 log T/K + 2.47 log
L/Lo. The dependence of the model mass-loss on the
pulsational period has explicitly been accounted for in connection with
the luminosity dependence, by applying an observed period--luminosity
relation for C-rich Miras. We also apply the improved mass-loss
description to our evolution models, and we revisit their tip-AGB
mass-loss histories and the total masses lost, in comparison to our
earlier work with a preliminary mass-loss description. While there is
virtually no difference for the models in the lower mass range of
consideration (Mi = 1.0 to \approx 1.3 Mo), we
now find more realistic, larger superwind mass-loss rates for larger
stellar masses: i.e., Mdot between ~ 0.4 and 1.0 x 10-4Mo/yr
for Mi between 1.85 and 2.65 Mo, removing between
0.6 and 1.2 Mo, respectively, during the final 30000 yrs on
the tip-AGB.
You can get this publication ...