Radial Distribution of the Dust Comae of Comets 45P/Honda-Mrkos-Pajdu\u{s}\'akov\'a and 46P/Wirtanen

TL;DR

This study analyzes the radial dust distribution in the comae of comets 45P/Honda-Mrkos-Pajdu
61e1kove1 and 46P/Wirtanen, revealing distinct dust environment characteristics and azimuthal dependencies through detailed observational data.

Contribution

It provides the first detailed radial profile analysis of these two comets' dust comae, highlighting differences in dust properties and azimuthal variations.

Findings

45P/HMP's radial profile slope changes from -1.81 to -0.35 around perihelion.

46P/Wirtanen's radial profile remains constant at about -1.05.

46P/Wirtanen's dust distribution depends on the solar position angle.

Abstract

There was an unprecedented opportunity to study the inner dust coma environment, where the dust and gas are not entirely decoupled, of comets 45P/Honda-Mrkos-Pajdu\u{s}\'akov\'a (45P/HMP) from Dec. 26, 2016 - Mar. 15, 2017, and 46P/Wirtanen from Nov. 10, 2018 - Feb. 13, 2019, both in visible wavelengths. The radial profile slopes of these comets were measured in the R and HB-BC filters most representative of dust, and deviations from a radially expanding coma were identified as significant. The azimuthally averaged radial profile slope of comet 45P/HMP gradually changes from -1.81 $\pm$ 0.20 at 5.24 days pre-perihelion to -0.35 $\pm$ 0.16 at 74.41 days post perihelion. Contrastingly, the radial profile slope of 46P/Wirtanen stays fairly constant over the observed time period at -1.05 $\pm$ 0.05. Additionally, we find that the radial profile of 46P/Wirtanen is azimuthally dependent on the skyplane-projected solar position angle, while that of 45P/HMP is not. These results suggest that comet 45P/HMP and 46P/Wirtanen have vastly different coma dust environments and that their dust properties are distinct. As evident from these two comets, well-resolved inner comae are vital for detailed characterization of dust environments.