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

©NASA STSCI

Interstellar Comet 2I/Borisov

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 H2O production rate of (6.3±1.5)×1026 mol s−1. Comparing to previously reported observations of CN, this implies a CN/H2O ratio of ∼0.3-0.9%. 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. C2/H2O is normal or depleted depending on interpretation of recent results pertaining to C2. The dust-to-gas ratio is consistent with the normal value for Solar System comets. Using a simple sublimation model we estimate an H2O active area of 1.7 km2, which for current estimates for the size of Borisov suggests active fractions between 1-150%, consistent with values measured in Solar System comets.

For the smallest size estimates our derived H2O production rates suggest Borisov may be hyperactive (> 100% of its surface active). However, these conclusions concerning active fraction are model dependent. More detailed characterization of 2I/Borisov, including compositional information and properties of the nucleus, are needed to fully interpret the observed H2O production rate.

Adam J. McKay, Anita L. Cochran, Neil Dello Russo, Michael DiSanti
(Submitted on 28 Oct 2019)
Comments: 7 pages, 2 figures, 1 table, submitted to ApJ Letters
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1910.12785 [astro-ph.EP] (or arXiv:1910.12785v1 [astro-ph.EP] for this version)
Submission history
From: Adam McKay
[v1] Mon, 28 Oct 2019 16:22:35 UTC (250 KB)
https://arxiv.org/abs/1910.12785
Astrobiology, Astrochemistry

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