The Impact of UV Radiation on Circumstellar Chemistry

Maryam Saberi*, Wouter Vlemmings, Tom Millar, Elvire De Beck

*Corresponding author for this work

Research output: Contribution to journalArticle


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).

Original languageEnglish
Pages (from-to)191-195
Number of pages5
JournalProceedings of the International Astronomical Union
Early online date30 Dec 2019
Publication statusEarly online date - 30 Dec 2019


  • Astrochemistry
  • Binaries: General
  • Radiative transfer
  • Stars: Abundances
  • Stars: Agb and post-agb
  • Stars: Carbon
  • Stars: Chromospheres
  • Stars: Circumstellar matter
  • Ultraviolet: Stars

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Astronomy and Astrophysics
  • Nutrition and Dietetics
  • Public Health, Environmental and Occupational Health
  • Space and Planetary Science

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