Astronomy and Astrophysics – Astronomy
Scientific paper
Oct 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999aps..4cf..ee05w&link_type=abstract
American Physical Society, Four Corners Section Fall Meeting, October 1-2, 1999 The University of Arizona Tucson, AZ, abstract #
Astronomy and Astrophysics
Astronomy
Scientific paper
The galactic interstellar extinction curve exhibits a pronounced feature at 217.5 nm. The most striking characteristic of this feature is the relatively fixed nature of its central wavelength, while the width of the feature may vary. Small graphite particles are often proposed as the carrier of this UV feature. However, graphite grains of a single size and shape cannot reproduce the observed width and peak characteristics simultaneously. Here, we investigate the extent to which these characteristics may be reproduced by manipulating the optical constants. The optical constants for graphite which are most commonly used by the astronomical community do not yield the narrowest 217.5 nm features observed. We have calculated three sets of optical constants for astronomical graphite such that, in each case, a different shape produces a feature with a peak at 217.5 nm and a width corresponding to the narrowest observed feature. Using grains in the Rayleigh approximation, we have calculated extinction curves for combinations of prolate, spherical, and oblate grain shapes, and have successfully reproduced the stationary nature of the peak. In addition, such shape variations do give variations in the width of the feature whose relative magnitudes match the observations. However, the absolute values of the calculated widths fall short by approximately 10 percent.
Aannestad Per
Will Lisa
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