Dust in Comet C/2007 N3 (Lulin)

TL;DR

This study combines optical, near-infrared polarimetry, and mid-infrared spectroscopy to analyze dust properties in comet C/2007 N3 (Lulin), revealing insights into its dust composition and structure.

Contribution

It provides the first combined polarimetric and mid-infrared spectral analysis of comet Lulin's dust, suggesting large, low-porosity aggregate particles as the main dust component.

Findings

Comet Lulin exhibits typical negative polarization in optical and near-infrared wavelengths.

The 10 micron silicate feature is weak, indicating a mixture of silicate and carbonaceous material.

Dust particles are best modeled as large, low-porosity aggregates.

Abstract

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.