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L. M. Will, P. A. Aannestad (Arizona State University)
The 2175 Å\ bump is the most prominent feature in the galactic interstellar extinction curve. The most striking characteristic of this feature is the stability of its peak wavelength while the width of the feature may vary along different lines of sight. Small graphite particles are frequently invoked as the carrier of the bump, but these dust grains alone cannot explain all of the observed behaviors. In this work, we investigate various carbonaceous materials (such as graphite, amorphous carbon, coals) in the form of dust grains with core-mantle, composite, and porous structures. This approach also incorporates the effects of grain shape and shape probability distributions to discern the impact on the 2175 Å\ feature.