Formation of polycyclic aromatic hydrocarbons in circumstellar envelopes

Journal Article · Thu Jun 01 00:00:00 EDT 1989 · Astrophysical Journal; (USA)

DOI:https://doi.org/10.1086/167501· OSTI ID:5711191

Frenklach, M; Feigelson, E D ^[1]

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1. Pennsylvania State Univ., University Park (USA)

Production 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. 87 refs.

• OSTI ID: 5711191
• Journal Information: Astrophysical Journal; (USA), Vol. 341; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
HYDROCARBONS
COSMOCHEMISTRY
STELLAR WINDS
CHEMICAL COMPOSITION
ABUNDANCE
AROMATICS
ASTROPHYSICS
CARBON
INTERSTELLAR SPACE
NUMERICAL SOLUTION
RED GIANT STARS
STARS
CHEMISTRY
ELEMENTS
GIANT STARS
NONMETALS
ORGANIC COMPOUNDS
SPACE
STELLAR ACTIVITY
640102* - Astrophysics & Cosmology- Stars & Quasi-Stellar
Radio & X-Ray Sources