Water, hydrogen cyanide, carbon monoxide, and dust production from distant comet 29P/Schwassmann-Wachmann 1

Abstract

29P/Schwassmann-Wachmann 1 is a distant Centaur/comet, showing persistent CO-driven activity and frequent outbursts. We used the Herschel space observatory in 2010, 2011, and 2013 to observe H${}_2$O and NH${}_3$ and to image the dust coma. Observations with the IRAM 30 m were undertaken in 2007, 2010, 2011, and 2021 to monitor the CO production rate and to search for HCN. Modeling was performed to constrain the size of the sublimating icy grains and to derive the dust production rate. HCN is detected for the first time in comet 29P (at 5$\sigma$ in the line area). H${}_2$O is detected as well, but not NH${}_3$. H${}_2$O and HCN line shapes differ strongly from the CO line shape, indicating that these two species are released from icy grains. CO production rates are in the range (2.9-5.6) $\times$ 10${}^{28}$ s${}^{-1}$ (1400--2600 kg s${}^{-1}$). A correlation between the CO production rate and coma brightness is observed, as is a correlation between CO and H${}_2$O production. The correlation obtained between the excess of CO production and excess of dust brightness with respect to the quiescent state is similar to that established for the continuous activity of comet Hale-Bopp. The measured $Q$(H${}_2$O)/$Q$(CO) and $Q$(HCN)/$Q$(CO) production rate ratios are 10.0 $\pm$ 1.5 % and 0.12 $\pm$ 0.03 %, respectively, averaging the April-May 2010 measurements ($Q$(H${}_2$O) = (4.1 $\pm$ 0.6) $\times$ 10${}^{27}$ s${}^{-1}$, $Q$(HCN) = (4.8 $\pm$ 1.1) $\times$ 10${}^{25}$ s${}^{-1}$). We derive three independent and similar values of the effective radius of the nucleus, $\sim$ 31 $\pm$ 3 km. The inferred dust mass-loss rates during quiescent phases are in the range 30-120 kg s${}^{-1}$, indicating a dust-to-gas mass ratio $<$ 0.1 during quiescent activity. We conclude that strong local heterogeneities exist on the surface of 29P, with quenched dust activity from most of the surface, but not in outbursting regions.

28 pages, 15 figures, A&A in press

References in corpus (11)

• Summer fireworks on comet 67P
• Water Ice and Dust in the Innermost Coma of Comet 103P/Hartley 2
• Terrestrial deuterium-to-hydrogen ratio in water in hyperactive comets
• Outburst activity in comets: II. A multi-band photometric monitoring of comet 29p/Schwassmann-Wachmann 1
• Evidence of sub-surface energy storage in comet 67P from the outburst of 2016 July 3
• A study of the distant activity of comet C/2006 W3 (Christensen) using Herschel and ground-based radio telescopes
• Photometric and spectroscopic analysis of Comet 29P/Schwassmann-Wachmann 1 activity
• Water production in comet 81P/Wild 2 as determined by Herschel/HIFI
• Data processing pipeline for Herschel HIFI
• Herschel observations of gas and dust in comet C/2006 W3 (Christensen) at 5 AU from the Sun
• Deep Herschel PACS point spread functions

Cited by in corpus (2)

• A link between the size and composition of comets
• Pre-perihelion Volatile Evolution of Interstellar Comet 3I/ATLAS Indicating Significant Contribution from Extended Source in the Coma