Analysis of CN Coma Morphology Features of Comet 21P/Giacobini-Zinner

TL;DR

This study analyzes jet features in Comet 21P/Giacobini-Zinner's coma during its 2018 perihelion to determine its rotational period, gas outflow velocity, and rotational pole orientation using narrowband CN imaging.

Contribution

It provides new measurements of the comet's rotational period, outflow velocities, and pole orientation based on morphological analysis of CN jet features.

Findings

Rotational period of approximately 7.39 or 10.66 hours.

Lower limit of outflow velocity around 730-740 m/s.

Northern jet exhibits a corkscrew morphology.

Abstract

We analyze jet features found in the coma of Comet 21P/Giacobini-Zinner (21P/GZ) during its 2018 perihelion passage using narrowband CN photometric imaging in order to determine the comet's rotational period, and constrain the CN gas outflow velocity and rotational state through the analysis of azimuthally enhanced morphological features. We find that 21P/GZ has a period of either 7.39 $\pm$ 0.01 or 10.66 $\pm$ 0.01 hours. We measure a lower limit to the outflow velocity for the Northern Jet of 730 $\pm$ 30 m s$^{-1}$ and for the Southern Jet of 740 $\pm$ 30 m s$^{-1}$. We analyze the morphologies of the jet features and determine that the Northern jet possesses a corkscrew pattern, and utilize that knowledge to determine a rotational pole position at a Right Ascension of ${169^{+28}_{-23}}^{\circ}$ and a Declination of ${73^{+5}_{-11}}^{\circ}$, with undetermined sense of rotation.