The formation of Polycyclic Aromatic Hydrocarbons in evolved circumstellar environments

Cherchneff, Isabelle. (2010) The formation of Polycyclic Aromatic Hydrocarbons in evolved circumstellar environments. In: PAHs and the Universe. pp. 177-189.

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Official URL: http://edoc.unibas.ch/51270/

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The formation of Polycyclic Aromatic Hydrocarbons in the circumstellar outflows of evolved stars is reviewed, with an emphasis on carbon stars on the Asymptotic Giant Branch. Evidence for PAHs present in their winds is provided by meteoritic studies and recent observations of the Unidentified Infrared bands. We detail the chemical processes leading to the closure of the first aromatic ring as well as the growth mechanisms leading to amorphous carbon grains. Existing studies on PAH formation in evolved stellar envelopes are reviewed and new results for the modelling of the inner wind of the archetype carbon star IRC+10216 are presented. Benzene, C 6 H 6 , forms close to the star, as well as water, H 2 O, as a result of non-equilibrium chemistry induced by the periodic passage of shocks. The growth process of aromatic rings may thus resemble that active in sooting flames due to the presence of radicals like hydroxyl, OH. Finally, we discuss possible formation processes for PAHs and aromatic compounds in the hydrogen-rich R CrB star, V854 Cen, and their implication for the carriers of the Red Emission and the Diffuse Interstellar Bands.
Faculties and Departments:05 Faculty of Science > Departement Physik > Physik
UniBasel Contributors:Cherchneff-Parrinello, Isabelle
Item Type:Conference or Workshop Item, refereed
Conference or workshop item Subtype:Conference Paper
Publisher:EDP Sciences
Series Name:EAS Publications Series
Note:Publication type according to Uni Basel Research Database: Conference paper
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Last Modified:15 Mar 2017 10:03
Deposited On:15 Mar 2017 10:03

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