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Catalogue POP – Notice individuelle de publication

Cordiner M. A., Boissier Jérémie, Charnley Steven B., Remijan Anthony J., Mumma Michael J., Villanueva Gerónimo L., Lis Darek C., Milam Stefanie N., Paganini Lucas, Crovisier Jacques, Bockelée-Morvan Dominique, Kuan Yi-Jehng, Coulson I. M.,

ALMA Mapping of Rapid Gas and Dust Variations in Comet C/2012 S1 (ISON):New Insights into the Origin of Cometary HNC

The Astrophysical Journal, 2017, vol. 838

Référence DOI : 10.3847/1538-4357/aa6590
Référence ADS : 2017ApJ...838..147C

Résumé :

Observations of the sungrazing comet C/2012 S1 (ISON) were carried out using the Atacama Large Millimeter/submillimeter Array at a heliocentric distance of 0.58-0.54 au (pre-perihelion) on 2013 November 16-17. Temporally resolved measurements of the coma distributions of HNC, CH<SUB>3</SUB>OH, H<SUB>2</SUB>CO, and dust were obtained over the course of about an hour on each day. During the period UT 10:10-11:00 on November 16, the comet displayed a remarkable drop in activity, manifested as a >42% decline in the molecular line and continuum fluxes. The H<SUB>2</SUB>CO observations are consistent with an abrupt, ≈50% reduction in the cometary gas production rate soon after the start of our observations. On November 17, the total observed fluxes remained relatively constant during a similar period, but strong variations in the morphology of the HNC distribution were detected as a function of time, indicative of a clumpy, intermittent outflow for this species. Our observations suggest that at least part of the detected HNC originated from degradation of nitrogen-rich organic refractory material, released intermittently from confined regions of the nucleus. By contrast, the distributions of CH<SUB>3</SUB>OH and H<SUB>2</SUB>CO during the November 17 observations were relatively uniform, consistent with isotropic outflow and stable activity levels for these species. These results highlight a large degree of variability in the production of gas and dust from comet ISON during its pre-perihelion outburst, consistent with repeated disruption of the nucleus interspersed with periods of relative quiescence.

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