J/A+A/626/A100 M-type AGB stars wind and dust models (Bladh+, 2019)
An extensive grid of DARWIN models for M-type AGB stars.
I. Mass-loss rates and other properties of dust-driven winds.
Bladh S., Liljegren S., Hoefner S., Aringer B., Marigo P.
<Astron. Astrophys. 626, A100 (2019)>
=2019A&A...626A.100B 2019A&A...626A.100B (SIMBAD/NED BibCode)
ADC_Keywords: Models, atmosphere ; Stars, late-type ; Stars, variable ;
Stars, M-type
Keywords: stars: AGB and post-AGB - stars: winds, outflows - stars: mass-loss -
stars: atmospheres - stars: evolution - stars: late-type
Abstract:
The stellar winds of asymptotic giant branch (AGB) stars are commonly
attributed to radiation pressure on dust grains, formed in the wake of
shock waves that arise in the stellar atmospheres. The mass loss due
to these outflows is substantial, and modelling the dynamical
properties of the winds is essential both for studies of individual
stars and for understanding the evolution of stellar populations with
low to intermediate mass.
The purpose of this work is to present an extensive grid of dynamical
atmosphere and wind models for M-type AGB stars, covering a wide range
of relevant stellar parameters.
We used the DARWIN code, which includes frequency-dependent
radiation-hydrodynamics and a time-dependent description of dust
condensation and evaporation, to simulate the dynamical atmosphere.
The wind-driving mechanism is photon scattering on submicron-sized
Mg2SiO4 grains. The grid consists of ∼4000 models, with luminosities
from L*=890L☉ to L*=40000 L☉ and effective temperatures
from 2200 to 3400K. For the first time different current stellar
masses are explored with M-type DARWIN models, ranging from
0.75M☉ to 3 M☉. The modelling results are radial
atmospheric structures, dynamical properties such as mass-loss rates
and wind velocities, and dust properties (e.g. grain sizes,
dust-to-gas ratios, and degree of condensed Si).
We find that the mass-loss rates of the models correlate strongly with
luminosity. They also correlate with the ratio L*/M*: increasing L*/M*
by an order of magnitude increases the mass-loss rates by about three
orders of magnitude, which may naturally create a superwind regime in
evolution models. There is, however, no discernible trend of mass-loss
rate with effective temperature, in contrast to what is found for
C-type AGB stars. We also find that the mass-loss rates level off at
luminosities higher than ∼14000L☉, and consequently at pulsation
periods longer than ∼800 days. The final grain radii range from 0.25
to 0.6um. The amount of condensed Si is typically between 10 and 40%,
with gas-to-dust mass ratios between 500 and 4000.
Description:
We present an extensive grid of dynamical atmosphere and wind models
for M-type AGB stars, covering a wide range of relevant stellar
parameters. We used the DARWIN code, which includes
frequency-dependent radiation- hydrodynamics and a time-dependent
description of dust condensation and evaporation, to simulate the
dynamical atmosphere. The wind-driving mechanism is photon scattering
on submicron-sized Mg2SiO4 grains. The models produce radial
snapshots of the atmospheric structure, dynamical properties
(mass-loss rates and wind velocities) and dust properties (grain
sizes, dust-to-gas ratios, and degree of condensed Si).
Fundamental model parameters (stellar, dust, and pulsation parameters)
and the resulting wind and dust characteristics for DARWIN models of
M-type AGB stars producing a stellar wind.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
mgridsol.dat 64 2120 Fundamental model parameters and the resulting
wind and dust characteristics
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Byte-by-byte Description of file: mgridsol.dat
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Bytes Format Units Label Explanations
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1- 4 F4.2 Msun Mass Current stellar mass
6- 9 F4.2 [Lsun] log(L) Stellar luminosity
11- 14 I4 K Teff Effective temperature
16- 19 I4 d Per Pulsation period
21- 23 F3.1 km/s up Piston velocity amplitude
25- 27 F3.1 --- fL Luminosity amplitude scaling factor
29- 33 F5.1 [-] log(nd/nH) Seed particle abundance
35- 42 E8.2 Msun/yr dM/dt Mass-loss rate
44- 47 F4.1 km/s uinf Wind velocity
49- 52 F4.2 um agr Grain radii
54- 57 F4.2 --- fSi Degree of condensed Si
59- 64 F6.1 --- gtd Gas-to-dust mass ratio
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Acknowledgements:
Sara Bladh, sara.bladh(at)physics.uu.se
(End) Sara Bladh [Uppsala univ., Sweden], Patricia Vannier [CDS] 09-May-2019