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Formation of polycyclic aromatic hydrocarbons in circumstellar envelopesProduction of polycyclic aromatic hydrocarbons in carbon-rich circumstellar envelopes was investigated using a kinetic approach. A detailed chemical reaction mechanism of gas-phase PAH formation and growth, containing approximately 100 reactions of 40 species, was numerically solved under the physical conditions expected in cool stellar winds. The chemistry is based on studies of soot production in hydrocarbon pyrolysis and combustion. Several first-ring and second-ring cyclization processes were considered. A linear lumping algorithm was used to describe PAH growth beyond the second aromatic ring. PAH production using this mechanism was examined with respect to a grid of idealized constant velocity stellar winds as well as several published astrophysical models. The basic result is that the onset of PAH production in the interstellar envelopes is predicted to occur within the temperature interval of 1100 to 900 K. The absolute amounts of the PAHs formed, however, are very sensitive to a number of parameters, both chemical and astrophysical, whose values are not accurately known. Astrophysically meaningful quantities of PAHs require particularly dense and slow stellar winds and high initial acetylene abundance. It is suggested that most of the PAHs may be produced in a relatively small fraction of carbon-rich red giants.
Document ID
19890054014
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Frenklach, Michael
(Pennsylvania State Univ. University Park, PA, United States)
Feigelson, Eric D.
(Pennsylvania State University University Park, United States)
Date Acquired
August 14, 2013
Publication Date
June 1, 1989
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 341
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
89A41385
Funding Number(s)
CONTRACT_GRANT: NAG3-668
CONTRACT_GRANT: NSF AST-83-51447
Distribution Limits
Public
Copyright
Other

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