Atmospheres and wind properties of non-spherical AGB stars
| Autor: | B. Freytag, Susanne Höfner, Sofie Liljegren, Sara Bladh |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
Shock wave
Physics 010308 nuclear & particles physics Astrophysics::High Energy Astrophysical Phenomena Stellar atmosphere FOS: Physical sciences Astronomy and Astrophysics Context (language use) Astrophysics 01 natural sciences Stars Astrophysics - Solar and Stellar Astrophysics Space and Planetary Science 0103 physical sciences Asymptotic giant branch Astrophysics::Solar and Stellar Astrophysics Astrophysics::Earth and Planetary Astrophysics 010303 astronomy & astrophysics Physics::Atmospheric and Oceanic Physics Astrophysics::Galaxy Astrophysics Solar and Stellar Astrophysics (astro-ph.SR) |
| DOI: | 10.48550/arxiv.1808.05043 |
| Popis: | The wind-driving mechanism of asymptotic giant branch (AGB) stars is commonly attributed to a two-step process: first, gas in the stellar atmosphere is levitated by shockwaves caused by stellar pulsation, then accelerated outwards by radiative pressure on newly formed dust, inducing a wind. Dynamical modelling of such winds usually assumes a spherically symmetric star. We explore the potential consequences of complex stellar surface structures, as predicted by three-dimensional (3D) star-in-a-box modelling of M-type AGB stars, on the resulting wind properties with the aim to improve the current wind models. Two different modelling approaches are used; the CO$^5$BOLD 3D star-in-a-box code to simulate the convective, pulsating interior and lower atmosphere of the star, and the DARWIN one-dimensional (1D) code to describe the dynamical atmosphere where the wind is accelerated. The gas dynamics of the inner atmosphere region at distances of $R\sim1-2R_\star$, which both modelling approaches simulate, are compared. Dynamical properties and luminosity variations derived from CO$^5$BOLD interior models are used as input for the inner boundary in DARWIN wind models in order to emulate the effects of giant convection cells and pulsation, and explore their influence on the dynamical properties. The CO$^5$BOLD models are inherently anisotropic, with non-uniform shock fronts and varying luminosity amplitudes, in contrast to the spherically symmetrical DARWIN wind models. DARWIN wind models with CO$^5$BOLD-derived inner boundary conditions produced wind velocities and mass-loss rates comparable to the standard DARWIN models, however the winds show large density variations on time-scales of 10-20 years. Comment: 13 pages, 12 figures, Accepted for publication in A&A |
| Databáze: | OpenAIRE |
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