Water production rates and activity of interstellar comet 2I/Borisov

Abstract

We observed the interstellar comet 2I/Borisov using the Neil Gehrels-Swift Observatory's Ultraviolet/Optical Telescope. We obtained images of the OH gas and dust surrounding the nucleus at six epochs spaced before and after perihelion (-2.56 AU to 2.54 AU). Water production rates increased steadily before perihelion from $(7.0\pm 1.5)\times 10^{26}$ molecules s${}^{-1}$ on Nov. 1, 2019 to $(10.7\pm 1.2)\times 10^{26}$ molecules s${}^{-1}$ on Dec. 1. This rate of increase in water production rate is quicker than that of most dynamically new comets and at the slower end of the wide range of Jupiter-family comets. After perihelion, the water production rate decreased to $(4.9\pm 0.9)\times 10^{26}$ molecules s${}^{-1}$ on Dec. 21, which is much more rapidly than that of all previously observed comets. Our sublimation model constrains the minimum radius of the nucleus to 0.37 km, and indicates an active fraction of at least 55% of the surface. $A(0)f\rho$ calculations show a variation between 57.5 and 105.6 cm with a slight trend peaking before the perihelion, lower than previous and concurrent published values. The observations confirm that 2I/Borisov is carbon-chain depleted and enriched in NH${}_2$ relative to water.

12 pages, 3 figures, 2 tables, submitted to ApJL

References in corpus (15)

• Initial characterization of interstellar comet 2I/Borisov
• Detection of exocometary CO within the 440 Myr-old Fomalhaut belt: a similar CO+CO${}_2$ ice abundance in exocomets and Solar System comets
• Seasonal Mass Transfer on the Nucleus of Comet 67P/Chuyumov-Gerasimenko
• 2I/Borisov: A C${}_2$ depleted interstellar comet
• Detection of CN gas in Interstellar Object 2I/Borisov
• The Nucleus of Interstellar Comet 2I/Borisov
• The Evolving Activity of the Dynamically Young Comet C/2009 P1 (Garradd)
• Detection of a Water Tracer in Interstellar Comet 2I/Borisov
• Changes in the physical environment of the inner coma of 67P/Churyumov-Gerasimenko with decreasing heliocentric distance
• Detection of Diatomic Carbon in 2I/Borisov
• Carbon Chain Depletion of 2I/Borisov
• Water Production Activity of Nine Long-Period Comets from SOHO/SWAN Observations of Hydrogen Lyman-alpha: 2013-2016
• The pre-perihelion activity of dynamically new comet C/2013 A1 (Siding Spring) and its close encounter with Mars
• Searching for water ice in the coma of interstellar object 2I/Borisov
• Diagnostics of collisions between electrons and water molecules in near-ultraviolet and visible wavelengths

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• The similarity of the interstellar comet 2I/Borisov to solar system comets from high resolution optical spectroscopy
• Activity of the first interstellar comet 2I/Borisov around perihelion: Results from Indian observatories
• Constraints on the Spin-Pole Orientation, Jet Morphology and Rotation of Interstellar Comet 2I/Borisov with Deep HST Imaging
• Very Large Telescope Observations of Interstellar Comet 3I/ATLAS. II. From Quiescence to Glow: Dramatic Rise of Ni i Emission and Incipient CN Outgassing at Large Heliocentric Distances*
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• Perihelion Asymmetry in the Water Production Rate of the Interstellar Object 3I/ATLAS
• Near-Discovery SOAR Photometry of the Third Interstellar Object: 3I/ATLAS
• Pre-perihelion radio observations of comet 12P/Pons-Brooks with Tianma radio telescope
• Constraining the orientation of the spin axes of extrasolar minor bodies 1I/2017 U1 (`Oumuamua) and 2I/Borisov
• Cometary science with CUBES
• Pre-perihelion Volatile Evolution of Interstellar Comet 3I/ATLAS Indicating Significant Contribution from Extended Source in the Coma
• Prospects for the Crossing of Comet 3I/ATLAS's Ion Tail