Aggregate dust model to describe polarization properties of Comet Hale-Bopp

作者：Das H S^*; Das S R; Sen A K

来源：Monthly Notices of the Royal Astronomical Society, 2008, 390(3): 1195-1199.

DOI：10.1111/j.1365-2966.2008.13822.x

• polarization
• scattering
• comets: general
• dust, extinction

In this work, the observed linear-polarization data of Comet Hale-Bopp are studied at wavelengths lambda = 0.485 and 0.684 mu m through simulations using Ballistic Particle-Cluster Aggregate and Ballistic Cluster-Cluster Aggregate. Using superposition T-MATRIX code, the best-fitting values of complex refractive indices are calculated which can well match the observed polarization data at the above two wavelengths. It is found from our analysis that there is not a single value of the monomer radius (a(m)) that can simultaneously fit the observed polarization data at two wavelengths 0.485 and 0.684 mu m. However, for different a(m) in the two wavelengths, corresponding to similar size parameter of the monomer (x approximate to 1.56), better fit can be achieved. The best-fitting complex refractive indices (n, k) coming out from this analysis are found to be (1.778, 0.059) at lambda = 0.485 mu m when a(m) = 0.12 mu m and (1.755, 0.080) at lambda = 0.684 mu m when a(m) = 0.17 mu m. The above values of refractive index show silicate behaviour as the values are close to amorphous olivine. Thus, it can be concluded that the silicate composition can best match the observed polarization data of Comet Hale-Bopp at lambda = 0.485 and 0.684 mu m. Finally, the polarization properties of Comet Hale-Bopp are compared with Comet Levy 1990XX.

• 出版日期2008-11-1