The Impact of UV Radiation on Circumstellar Chemistry
Journal article, 2019

© International Astronomical Union 2019. UV radiation plays a critical role in the chemistry of circumstellar envelopes (CSEs) around evolved stars on the asymptotic giant branch (AGB). However, the effects of all potential sources of UV radiation have not been included in models. We present preliminary results of adding an internal source of UV to the CSE chemistry and predict large enhancements of atomic and ionic species arising from photo-destruction of parent species. Observations of atomic carbon towards the UV-bright AGB star o Cet are consistent with the modelling. In addition, we calculate the precise depth dependence of the CO photodissociation rate in an expanding CSE. We incorporate this within a chemical network active in the outflows of AGB stars, which includes 933 species and 15182 reactions. Our results show that the CO envelope size is about 30% smaller at half abundance than the most commonly used radius reported by Mamon et al. (1988).

Astrochemistry

Stars: Agb and post-agb

Radiative transfer

Stars: Carbon

Ultraviolet: Stars

Stars: Abundances

Stars: Chromospheres

Stars: Circumstellar matter

Binaries: General

Author

Maryam Saberi

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics, Galactic Astrophysics

Wouter Vlemmings

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics, Galactic Astrophysics

T.J. Millar

Queen's University Belfast

Elvire de Beck

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics, Galactic Astrophysics

Proceedings of the International Astronomical Union

1743-9213 (ISSN) 1743-9221 (eISSN)

191-195

Subject Categories

Astronomy, Astrophysics and Cosmology

Ecology

Other Physics Topics

DOI

10.1017/S1743921318005483

More information

Latest update

1/20/2020