Detection of a Water Tracer in Interstellar Comet 2I/Borisov

Abstract

We present high spectral resolution optical spectra obtained with the ARCES instrument at Apache Point Observatory showing detection of the [OI]6300 A line in interstellar comet 2I/Borisov. We employ the observed flux in this line to derive an H${}_2$O production rate of (6.3$\pm$1.5)$\times$10${}^{26}$ mol s${}^{-1}$. Comparing to previously reported observations of CN, this implies a CN/H${}_2$O ratio of $\sim$0.3-0.6%. The lower end of this range is consistent with the average value in comets, while the upper end is higher than the average value for Solar System comets, but still within the range of observed values. C${}_2$/H${}_2$O is depleted, with a value likely less than 0.1%. The dust-to-gas ratio is consistent with the normal value for Solar System comets. Using a simple sublimation model we estimate an H${}_2$O active area of 1.7 km${}^2$, which for current estimates for the size of Borisov suggests active fractions between 1-150%, consistent with values measured in Solar System comets. More detailed characterization of 2I/Borisov, including compositional information and properties of the nucleus, is needed to fully interpret the observed H${}_2$O production rate.

8 pages, 2 figures, 1 table, Accepted in ApJ Letters

References in corpus (9)

• Initial Characterization of Interstellar Comet 2I/2019 Q4 (Borisov)
• Terrestrial deuterium-to-hydrogen ratio in water in hyperactive comets
• 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)
• Coupled Chemistry-Emission Model for Atomic Oxygen Green and Red-doublet Emissions in Comet C/1996 B2 Hyakutake
• Evolution of H${}_2$O, CO, and CO${}_2$ Production in Comet C/2009 P1 Garradd During the 2011-2012 Apparition
• The Unusual Spectrum of Comet 96P/Machholz

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• Exocomets from a Solar System Perspective
• Outburst and Splitting of Interstellar Comet 2I/Borisov
• Coma Anisotropy and the Rotation Pole of Interstellar Comet 2I/Borisov
• Gaseous atomic nickel in the coma of interstellar comet 2I/Borisov
• Visible and near-infrared observations of interstellar comet 2I/Borisov with the 10.4-m GTC and the 3.6-m TNG telescopes
• The similarity of the interstellar comet 2I/Borisov to solar system comets from high resolution optical spectroscopy
• X-SHOOTER Spectrum of Comet 3I/ATLAS: Insights into a Distant Interstellar Visitor
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• Coma environment of comet C/2017 K2 around the water ice sublimation boundary observed with VLT/MUSE
• Capture of interstellar objects II: by the Solar system
• Pre-perihelion Monitoring of Interstellar Comet 2I/Borisov
• Near-Discovery SOAR Photometry of the Third Interstellar Object: 3I/ATLAS
• Ionic emissions and activity evolution in comet C/2020 F3 (NEOWISE): Insights from long-slit spectroscopy and photometry
• Cometary science with CUBES
• Interstellar Object 3I/ATLAS Observed from Mars by China's Tianwen-1 Spacecraft