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  • 标题:Observations of Jupiter Family Comet 252P/LINEAR During a Close Approach to Earth Reveal Large Abundances of Methanol and Ethane
  • 本地全文:下载
  • 作者:L. Paganini ; M. N. Camarca ; M. J. Mumma
  • 期刊名称:The Astronomical journal
  • 印刷版ISSN:0004-6256
  • 电子版ISSN:1538-3881
  • 出版年度:2019
  • 卷号:158
  • 期号:3
  • 页码:1-9
  • DOI:10.3847/1538-3881/ab289c
  • 语种:English
  • 出版社:American Institute of Physics
  • 摘要:We observed short-period comet 252P/LINEAR post-perihelion during its 2016 passage, which presented a favorable opportunity to survey its chemical composition at a close Earth approach (∼0.14 au). We characterized the cometʼs chemical composition on four dates (UT 2016 April 12, 19, 26, and 29) using spectroscopic measurements with the Near-infrared Spectrograph (NIRSPEC) at the Keck Observatory on Maunakea, HI. Our high-resolution infrared spectra yielded production rates for four species (H 2 O, CH 3 OH, C 2 H 6 , and HCN) and upper limits for five species (NH 3 , H 2 CO, C 2 H 2 , CO, and CH 4 ). We measured water at an average production rate of 4.9±0.1×10 27 molec s −1 . The chemical properties of 252P suggest a rather typical composition, yet somewhat enriched in methanol and ethane but low in formaldehyde (upper limit) compared to other short-period comets surveyed at infrared wavelengths. Analysis of the ortho/para ratio in water indicates a nuclear spin temperature larger than∼38 K, consistent with statistical equilibrium (2σ). Spatial distributions of gases, which are representative of possible heterogeneity in the nucleus and/or gas dynamics upon sublimation, showed rather symmetric profiles, with subtle enhancements of the more volatile species C 2 H 6 and HCN toward the sunward hemisphere, while water showed spatial distributions that were extended toward the anti-sunward hemisphere. The continuum was characterized by a narrow distribution. We place our infrared results in the context of observations with the Discovery Channel Telescope, the James Clerk Maxwell submillimeter Telescope, and the Hubble Space Telescope.
  • 关键词:comets: general;comets: individual (252P/LINEAR);infrared: planetary systems;techniques: spectroscopic
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