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J/A+A/361/641      Investigation of mass loss mechanism of LPVs (Winters+, 2000)

A systematic investigation of the mass loss mechanism in dust forming long-period variable stars Winters J.M., Le Bertre T., Jeong K.S., Helling C., Sedlmayr E. <Astron. Astrophys. 361, 641 (2000)> =2000A&A...361..641W
ADC_Keywords: Stars, variable ; Mass loss ; Models, atmosphere Keywords: hydrodynamics - stars: winds, outflows - stars: carbon - stars: circumstellar matter - stars: mass-loss - stars: AGB and post-AGB Abstract: In order to investigate the relations between the mass loss from pulsating red giants and quantities which can be obtained from observations, we have explored the behavior of theoretical models which treat the time-dependent hydrodynamics of circumstellar outflows, including a detailed treatment of the dust formation process. This approach, while ignoring effects such as a possible non-sphericity of the stellar atmospheres which are difficult to assess, accounts correctly for factors such as the grain formation and destruction which are crucial to the mass-loss mechanism. We built a grid of ∼150 models covering a wide range of physical situations. This grid allows us to characterize the effects of different parameters, such as the stellar luminosity and temperature, the period and the amplitude of the pulsation, and the C/O element abundance ratio, on the behavior of AGB winds and on the rates of mass loss. We find two regimes for the stellar outflows. Description: Parameters and resultant quantities of a grid of hydrodynamical models for the circumstellar dust shells around pulsating red giants which treat the time-dependent hydrodynamics and include a detailed treatment of the dust formation process. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 86 298 Parameters and resultant quantities of the models table2.tex 99 925 LaTeX version of table 2
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 12 A12 --- Model Model name (1) 14- 16 F3.1 solMass M* Stellar mass 18- 21 F4.2 10+4solLum L* Stellar luminosity 23- 26 I4 K T* Stellar temperature 28- 31 F4.2 --- C/O Carbon-to-oxygen ratio 33- 36 I4 d P Pulsation period 38- 40 F3.1 km/s Dvp Pulsation amplitude 42- 49 E8.1 solMass/yr <dM/dt> ? Average mass loss rate 51- 55 F5.2 --- e_<dM/dt> ? Relative standard deviation of dM/dt 57- 60 F4.1 km/s <v{inf}> ? Average outflow velocity 62- 64 F3.1 10-3 Dust/Gas ? Average dust-to-gas mass ratio 66- 69 F4.2 --- K-L' ? Average K-L' color index 71- 86 A16 --- Type Type of model (2)
Note (1): the footnote symbols are: 0: Maron (1990Ap&SS.172...21M) x: AC1, Rouleau & Martin (1991ApJ...377..526R) D: Edoh (1983, Ph. D. Thesis, University of Arizona, (E)) Note (2): Model type (Sect. 3.1): A: Models with <α>t>1, dM/dt<3*10-7M/yr AB: Models with <α>t<1, dM/dt>10-6M/yr B: Models with <α>t=1, dM/dt<3*10-7M/yr "static state": The mass loss of these models is decreasing steadily with time and the velocity is approaching zero, i.e. the circumstellar shell is approaching a static state after a transition phase, where material is falling back to the star. no wind: Models that do not develop a wind structure
Acknowledgements: Jan Martin Winters
(End) Patricia Bauer [CDS] 29-Sep-2000
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