J/A+A/673/A21 Synthetic photometry for carbon-rich giants. V. (Eriksson+, 2023)
Synthetic photometry for carbon-rich giants.
V. Effects of grain size-dependent dust opacities.
Eriksson K., Hoefner S., Aringer B.
<Astron. Astrophys. 673, A21 (2023)>
=2023A&A...673A..21E 2023A&A...673A..21E (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Stars, giant ; Models ; Spectrophotometry
Keywords: stars: AGB and post-AGB - stars: carbon - stars: winds, outflows
Abstract:
The properties and the evolution of Asymptotic Giant Branch (AGB)
stars are strongly influenced by their mass loss through a stellar
wind. This, in turn, is believed to be caused by radiation pressure
due to the absorption and scattering of the stellar radiation by the
dust grains formed in the atmosphere. The optical properties of dust
are often estimated using the Small Particle Limit (SPL)
approximation, and it has been used frequently in modelling AGB
stellar winds when performing RHD (Radiation-HydroDynamics)
simulations.
Here we investigate the effects of replacing the SPL approximation by
detailed Mie calculations of the size-dependent opacities for grains
of amorphous carbon forming in C-rich AGB star atmospheres. We have
performed RHD simulations for a large grid of carbon star
atmosphere+wind models with different effective temperatures,
luminosities, stellar masses, carbon excesses and pulsation
properties. Also, a posteriori radiative transfer calculations for
many radial structures (snapshots) of these models were done resulting
in spectra and filter magnitudes.
We find that, when giving up the SPL approximation, the wind models
become more strongly variable, more dominated by gusts, although the
average mass-loss rates and outflow speeds are not changed much; the
increased radiative pressure on the dust throughout its formation zone
does however result in smaller grains and lower condensation fractions
(and thus higher gas-to-dust ratios). The photometric K magnitudes are
generally brighter, but at V the effects of using size-dependent dust
opacities are more complex: brighter for low mass-loss rates and
dimmer for massive stellar winds. Given the large effects on spectra
and photometric properties, it is necessary to use the detailed dust
optical data instead of the simple SPL approximation in stellar
atmosphere+wind modelling where dust is formed.
Description:
A table with photometric and dynamic properties of the models in the
grid is found here.
The models are arranged in increasing effective temperature,
luminosity, and stellar mass.
For each such combination the data are ordered by increasing carbon
excess, and piston velocity amplitude. In each line, after the model
parameters we list the log g (surface gravity in cgs units).
Then come dynamic quantities evaluated at the outer boundary:
mass-loss rate (in solar masses per year), the wind velocity (km/s),
the carbon condensation degree, and the dust-to-gas ratio. Note that
all given values are temporal means, see Sect. 3. Then follow the
photometric properties: the (full) amplitude of the bolometric
magnitude, the mean V magnitude, the range of V magnitudes, the mean K
magnitude and its range, and finally the colours (V-I), (V-K), (J-H)
and (H-K).
The luminosities and stellar masses are given in solar units.
The carbon excesses, log(N(C)-N(O))+12 are given on the scale where
logN(H)=12.00.
The piston velocity amplitudes, Delta(u_p), are given in km/s.
All the photometric quantities are given in magnitudes.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablec1.dat 102 268 Photometric and dynamic properties of
the models in the present grid
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See also:
J/A+A/503/913 : Synthetic spectrophotometry for C-rich giants (Aringer+, 2009)
J/A+A/566/A95 : C-rich giants synthetic spectrophotometry. IV (Eriksson+, 2014)
Byte-by-byte Description of file: tablec1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 K Teff Effective temperature
6- 9 F4.2 [Lsun] logL* log Luminosity
11- 14 F4.2 [Msun] M* Stellar mass
16- 18 F3.1 [-] Cex log carbon excess = log(C-O)+12
20 I1 km/s Dup Piston velocity amplitude
22- 26 F5.2 [cm/s2] logg log Surface gravity
28- 33 F6.2 [Msun/yr] logMdot ?=- log mean mass-loss rate
35- 38 F4.1 km/s uinf ?=- Mean outflow velocity
40- 44 F5.3 --- fc ?=- Mean carbon condensation degree
46- 53 E8.3 --- d/g ?=- Mean dust-to-gas ratio
55- 58 F4.2 mag DMbol Bolometric magnitude amplitude
60- 64 F5.2 mag Vmag Mean V magnitude
66- 70 F5.2 mag DVmag Amplitude in V (min-max)
72- 76 F5.2 mag Kmag Mean K magnitude
78- 81 F4.2 mag DKmag Amplitude in K (min-max)
83- 86 F4.2 mag V-I Mean (V-I) colour
88- 92 F5.2 mag V-K Mean (V-K) colour
94- 97 F4.2 mag J-H Mean (J-H) colour
99-102 F4.2 mag H-K Mean (H-K) colour
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Acknowledgements:
Kjell Eriksson, kjell.eriksson(at)physics.uu.se
References:
Aringer et al., Paper I 2009A&A...503..913A 2009A&A...503..913A, Cat. J/A+A/503/913
Nowotny et al., Paper II 2011A&A...529A.129N 2011A&A...529A.129N
Nowotny et al., Paper III 2013A&A...552A..20N 2013A&A...552A..20N
Eriksson et al., Paper IV 2014A&A...566A..95E 2014A&A...566A..95E, Cat. J/A+A/566/A95
(End) Patricia Vannier [CDS] 06-Mar-2023