The Formation of PAHs in Carbon Star Atmospheres

Session 67 - Stars: Evolution, Atmospheres, Intrinsic.
Display session, Thursday, June 11
Atlas Ballroom,

[67.17] The Formation of PAHs in Carbon Star Atmospheres

J. W. Ferguson, D. R. Alexander, F. Allard (Wichita State U.), H. R. Johnson (Indiana U.)

Polycyclic Aromatic Hydrocarbons (PAHs) have been suggested as the source of the diffuse interstellar bands, and may serve as a link in the formation of grains from complex molecules in atmospheres of carbon-rich stars. If PAHs exist in interstellar clouds, then where do they form? The most obvious answer would seem to be in the atmospheres of carbon stars, where the stellar wind may eject them into the interstellar medium. Recently Helling et al. (1996, Aamp;A, 315, 194) computed the fraction of carbon contained within PAHs for several carbon-rich stellar atmospheres. They conclude that PAHs are not significant in their hydrostatic atmospheres, that they may form in dynamical atmospheres, but that the resident time of the PAHs in those atmosphere may be insufficient for a significant amount of PAHs to form before being ejected. We extend the calculations of Helling et al. to much lower temperatures and lower densities, and investigate whether significant amounts of PAHs form in those outer layers.

This research was supported by NASA EPSCoR grant NCC5-168 and NASA LTSA grant NAG5-3435 to Wichita State University.

Program listing for Thursday