Water Production Rates from SOHO/SWAN Observations of Six comets: 2017-2020

TL;DR

This study analyzes water production rates of six Oort Cloud comets observed by SOHO/SWAN from 2017 to 2020, revealing breakup events and variations in activity related to their dynamical classes.

Contribution

First comprehensive analysis of water production rates for six comets using SOHO/SWAN data, including breakup events and activity variations.

Findings

C/2019 Y4 (ATLAS) and C/2020 F8 (SWAN) broke up before perihelion

Water production rates vary with comet dynamical class

Breakup events correlate with increased activity or disintegration

Abstract

The Solar Wind ANisotropies (SWAN) all-sky hydrogen Lyman-alpha camera on the SOlar and Heliosphere Observer (SOHO) satellite makes daily images of the entire sky to monitor the three-dimensional distribution of solar wind and solar radiation via its imprint on the stream of interstellar hydrogen that flows through the solar system. In the process it also records the distribution of the hydrogen comae of comets. We report here the analyses of six comets originally from the Oort Cloud observed during the 2017-2020 period by SWAN: C/2015 V2 (Johnson), C/2019 Y1 (ATLAS), C/2017 T2 (PanSTARRS), C/2020 F8 (SWAN), C/2019 Y4 (ATLAS), and C/2019 U6 (Lemmon). Of these the nuclei of C/2019 Y4 (ATLAS) and C/2020 F8 (SWAN) both broke up on their inbound orbit before perihelion. The water production rates over the detectable portion of each comet's orbit are determined and discussed in light of the comet's dynamical sub-class of Oort Cloud comets.