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Determining the effect of a non-uniform AGB outflow on its chemistry

Published online by Cambridge University Press:  04 September 2018

M. Van de Sande ,
J. O. Sundqvist ,
T. J. Millar  and
L. Decin
M. Van de Sande
Affiliation:
Department of Physics and Astronomy, Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium email: [email protected]
J. O. Sundqvist
Affiliation:
Department of Physics and Astronomy, Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium email: [email protected]
T. J. Millar
Affiliation:
School of Mathematics and Physics, Queens University Belfast, University Road, Belfast BT7 1NN, UK
L. Decin
Affiliation:
Department of Physics and Astronomy, Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium email: [email protected]
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Abstract

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The molecular composition of the stellar outflows of AGB stars is determined by the stellar elemental carbon-to-oxygen abundance ratio, together with the physical circumstances in the innermost region of the outflow. Near the stellar surface, thermal equilibrium (TE) can be assumed. This leads to a certain molecular composition with a O- or C-rich signature. However, several molecular species have been detected that are not expected to be present in the inner region under the assumption of TE chemistry. As a solution to explain the presence of these unexpected species, non-equilibrium chemistry in the inner region of the outflow has been proposed. The outflows of AGB stars are generally not spherically symmetric or homogeneous, which influences the penetration of interstellar UV photons throughout the outflow. We investigate the effect of a clumpy, non-homogeneous outflow on the composition of the inner region by introducing a simple porosity formalism in our chemical model.

Keywords

astrochemistrymolecular processesstars: AGB and post-AGBcircumstellar matterstars: mass loss
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 13 , Symposium S332: Astrochemistry VII: Through the Cosmos from Galaxies to Planets , March 2017 , pp. 43 - 46
Copyright
Copyright © International Astronomical Union 2018 

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