34.09

Thermal IR Spectral Synthesis and a Successful Application: The 8-13 micron spectrum of C/Hale-Bopp

R. W. Russell*, D. K. Lynch*, A. L. Mazuk, G. S. Rossano (The Aerospace Corporation), M. S. Hanner* (Jet Propulsion Laboratory), M. L. Sitko* (Univ. of Cincinnati)

A simple, physically realistic model for cometary dust emission in the thermal infrared from 8-13 microns which is based on the laboratory emissivity curves (Stephens and Russell, 1979) of the likely grain materials has been developed. The materials included (olivine (Fe Mg ) SiO enstitate (Fe Mg )SiO composition) are those shown by condensation theory to condense first in a cooling outflow around late-type stars, and are included with a grey body component to represent the continuum. Crystallinity, temperature, and relative amounts of the materials are the variables, and the results of the application of the model to Hale-Bopp data will be shown. The time dependencies of the amounts of the grain components and the contrast of the silicate feature are explored through the use of the model. The first clear relationship between the interstellar medium and cometary (solar system) dust is established via the model.

*Visiting Astronomer at the Infrared Telescope Facility, operated by the University of Hawaii under contract with the National Aeronautics and Space Administration.