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Lumpy stars and bumpy winds

Published online by Cambridge University Press:  30 December 2019

Sofie Liljegren Open the ORCID record for Sofie Liljegren [Opens in a new window] ,
Susanne Höfner ,
Bernd Freytag  and
Sara Bladh
Sofie Liljegren
Affiliation:
Division of Astronomy and Space Physics, Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden email: sofie.liljegren@physics.uu.se
Susanne Höfner
Affiliation:
Division of Astronomy and Space Physics, Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden email: sofie.liljegren@physics.uu.se
Bernd Freytag
Affiliation:
Division of Astronomy and Space Physics, Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden email: sofie.liljegren@physics.uu.se
Sara Bladh
Affiliation:
Division of Astronomy and Space Physics, Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden email: sofie.liljegren@physics.uu.se
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Abstract

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The wind-driving process of AGB stars is thought to be a two-step process: first matter is levitated by shock waves, and then accelerated outwards by radiation pressure on newly condensed dust grains. When modelling such a wind, spherical symmetry is usually assumed. This is in stark contrast with recent observations, which shows significant non-spherical structures. Giant convection cells cover the surface of the star, and matter is being ejected into the atmosphere where it condenses into lumpy dust clouds. We try to quantify the differences between what is simulated in the 3D star-in-a-box models (CO5BOLD code) and the 1D dynamical atmosphere and wind models (DARWIN code). The impact of having a non-spherical star on the wind properties is also investigated. We find that the inherent non-spherical behaviour of AGB stars might induce a dust-driven weak wind already early on the AGB, and including that the star is anisotropic when simulating the wind leads to large time variations in the density of the outflow. Such variations might be observable as small-scale structures in the circumstellar envelope.

Keywords

Evolved starsAGB starsStellar winds
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 14 , Symposium S343: Why Galaxies Care About AGB Stars: A Continuing Challenge through Cosmic Time , August 2018 , pp. 134 - 138
Copyright
© International Astronomical Union 2019 

References

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