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Improvements in the Computation of Grain Opacity

Published online by Cambridge University Press:  12 April 2016

David R. Alexander  and
Jason W. Ferguson
David R. Alexander
Affiliation:
Physics Department, Wichita State University, Wichita, Kansas 67260 USA
Jason W. Ferguson
Affiliation:
Department of Physics & Astronomy, University of Kentucky, Lexington, Kentucky 40506 USA

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Atoms and ions dominate the opacity of most astrophysical plasmas at temperatures above about 5000 K. In the range between 5000 K and about 1500 K, molecular processes are important contributors to the opacity. Depending upon the composition and pressure, grains may begin to condense at temperatures below about 1500 K. For the conditions of interest here, the grains which form are generally small (radius < 0.25 µm) compared to the wavelength of light near the peak of the Planck curve. Because their absorption and scattering cross section is so large compared to atoms or molecules, grains dominate the mean opacity whenever they are present and must, therefore, be taken into account whenever such temperatures are encountered. Our calculations indicate that failure to do so can lead to errors as large as five orders of magnitude in the mean opacity.

Type
Research Article
Information
International Astronomical Union Colloquium , Volume 146: Molecules in the Stellar Environment , 1994 , pp. 149 - 162
Copyright
Copyright © Springer-Verlag 1994

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