{sup 14}NH{sub 2}/{sup 15}NH{sub 2} RATIO IN COMET C/2012 S1 (ISON) OBSERVED DURING ITS OUTBURST IN 2013 NOVEMBER

Journal Article · Thu Feb 20 04:00:00 EST 2014 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/782/2/L16· OSTI ID:22363987

Shinnaka, Yoshiharu; Kawakita, Hideyo; Kobayashi, Hitomi; Nagashima, Masayoshi ^[1]

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1. Koyama Astronomical Observatory, Kyoto Sangyo University, Motoyama, Kamitamo, Kita, Kyoto 603-8555 (Japan)

We performed high-dispersion optical spectroscopic observations of comet C/2012 S1 (ISON) using the High Dispersion Spectrograph (R = 72,000) at the Subaru Telescope on UT 2013 November 15.6, during an outburst that started on UT 2013 November 14. Due to the high gas-production rate of NH{sub 2} during the outburst, we successfully detected weak emission lines of {sup 15}NH{sub 2} and many strong emission lines of {sup 14}NH{sub 2} in the optical wavelength region from 5500 to 8200 Å. The ratio of {sup 14}NH{sub 2}/{sup 15}NH{sub 2} is derived to be 139 ± 38 in comet C/2012 S1 (ISON). This ratio is close to that recently revealed based on the averaged spectrum of 12 comets, ∼130. This is also comparable to the typical cometary isotopic ratio of CN ({sup 12}C{sup 14}N/{sup 12}C{sup 15}N, observed in optical) and HCN (H{sup 12}C{sup 14}N/H{sup 12}C{sup 15}N, observed in radio), ∼150. However, these ratios are much smaller than the protosolar value, {sup 14}N/{sup 15}N = 441 ± 5. Because NH{sub 2} is considered to be a photodissociation product of NH{sub 3} in cometary coma, our result implies the occurrence of {sup 15}N fractionation of NH{sub 3} in the solar nebula or in the presolar molecular cloud.

• OSTI ID: 22363987
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 2 Vol. 782; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
AMMONIA
ASTRONOMY
ASTROPHYSICS
CARBON 12
CARBON NITRIDES
COMETS
COMPARATIVE EVALUATIONS
DISSOCIATION
EMISSION SPECTRA
INTERSTITIAL HELIUM GENERATION
INTERSTITIAL HYDROGEN GENERATION
ISOTOPE RATIO
MOLECULES
NITROGEN 14
NITROGEN 15
SOLAR NEBULA
TELESCOPES