Near-infrared Spectroscopic Observations of Comet C/2013 R1 (Lovejoy) by WINERED: CN Red-system Band Emission

Although high-resolution spectra of the CN red-system band are considered useful in cometary sciences, e.g., in the study of isotopic ratios of carbon and nitrogen in cometary volatiles, there have been few reports to date due to the lack of high-resolution (R λ/Δλ > 20,000) spectrographs in the...

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Bibliographic Details
Published in:The Astronomical journal 2017-08, Vol.154 (2), p.45
Main Authors: Shinnaka, Yoshiharu, Kawakita, Hideyo, Kondo, Sohei, Ikeda, Yuji, Kobayashi, Naoto, Hamano, Satoshi, Sameshima, Hiroaki, Fukue, Kei, Matsunaga, Noriyuki, Yasui, Chikako, Izumi, Natsuko, Mizumoto, Misaki, Otsubo, Shogo, Takenaka, Keiichi, Watase, Ayaka, Kawanishi, Takafumi, Nakanishi, Kenshi, Nakaoka, Tetsuya
Format: Article
Language:English
Subjects:
ASTRONOMY
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
CARBON
CARBON 12
CARBON 13
COMETS
comets: general
comets: individual (C/2013 R1 (Lovejoy))
EMISSION SPECTRA
EXCITATION
FLUORESCENCE
instrumentation: spectrographs
ISOTOPE RATIO
JAPAN
MIXING RATIO
NITROGEN
NITROGEN 14
NITROGEN 15
RESOLUTION
TELESCOPES
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Summary:Although high-resolution spectra of the CN red-system band are considered useful in cometary sciences, e.g., in the study of isotopic ratios of carbon and nitrogen in cometary volatiles, there have been few reports to date due to the lack of high-resolution (R λ/Δλ > 20,000) spectrographs in the near-infrared region around ∼1 m. Here, we present the high-resolution emission spectrum of the CN red-system band in comet C/2013 R1 (Lovejoy), acquired by the near-infrared high-resolution spectrograph WINERED mounted on the 1.3 m Araki telescope at the Koyama Astronomical Observatory, Kyoto, Japan. We applied our fluorescence excitation models for CN, based on modern spectroscopic studies, to the observed spectrum of comet C/2013 R1 (Lovejoy) to search for CN isotopologues (13C14N and 12C15N). We used a CN fluorescence excitation model involving both a "pure" fluorescence excitation model for the outer coma and a "fully collisional" fluorescence excitation model for the inner coma region. Our emission model could reproduce the observed 12C14N red-system band of comet C/2013 R1 (Lovejoy). The derived mixing ratio between the two excitation models was 0.94(+0.02/−0.03):0.06(+0.03/−0.02), corresponding to the radius of the collision-dominant region of ∼800-1600 km from the nucleus. No isotopologues were detected. The observed spectrum is consistent, within error, with previous estimates in comets of 12C/13C (∼90) and 14N/15N (∼150).
ISSN:0004-6256
1538-3881
1538-3881
DOI:10.3847/1538-3881/aa7576