We report optical imaging, optical and near-infrared polarimetry, and Spitzer mid-infrared spectroscopy of comet C/2007 N3 (Lulin). Polarimetric observations were obtained in R (0.676 micron) at phase angles from 0.44 degrees to 21 degrees with simultaneous observations in H (1.65 micron) at 4.0 degrees, exploring the negative branch in polarization. Comet C/2007 N3 (Lulin) shows typical negative polarization in the optical as well as a similar negative branch near-infrared wavelengths. The 10 micron silicate feature is only weakly in emission and according to our thermal models, is consistent with emission from a mixture of silicate and carbon material. We argue that large, low-porosity (akin to Ballistic Particle Cluster Aggregates) rather absorbing aggregate dust particles best explain both the polarimetric and the mid-infrared spectral energy distribution.
@article{arxiv.1103.0593,
title = {Dust in Comet C/2007 N3 (Lulin)},
author = {Charles E. Woodward and Terry Jay Jones and Bailey Brown and Erin Lee Ryan and Megan Krejny and Ludmilla Kolokolova and Michael S. Kelley and David E. Harker and Michael L. Sitko},
journal= {arXiv preprint arXiv:1103.0593},
year = {2015}
}