Cyanide chemistry in comet Hale-Bopp (C/1995 O1)

L. M. Ziurys, C. Savage, M. A. Brewster, A. J. Apponi, T. C. Pesch, S. Wyckoff

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Observations of comet Hale-Bopp (C/1995 O1) have been carried out near perihelion (1997 March) at millimeter wavelengths using the NRAO 12 m telescope. The J = 1 → 0, 2 → 1, and 3 → 2 lines of HCN at 88, 177, and 265 GHz were measured in the comet as well as the J = 3 → 2 lines of H13CN, HC15N, and HNC. The N = 2 → 1 transition of CN near 226 GHz was also detected, and an upper limit was obtained for the J = 2 → 1 line of HCNH+. From the measurements, column densities and production rates have been estimated. A column density ratio of [HCN]/[HNC] = 7 ± 1 was observed near perihelion, while it was found that [HCN]/[HCNH+] ≳ 1. The production rates at perihelion for HCN and CN were estimated to be Q(HCN) ∼ 1 × 1028 s-1 and Q(CN) ∼ 2.6 × 1027 s-1, respectively, resulting in a ratio of [HCN]/[CN] ≃ 3. Consequently, HCN is sufficiently abundant to be the parent molecule of CN in Hale-Bopp, and HCNH+ could be a source of HNC. Finally, carbon and nitrogen isotope ratios of 12C/13C = 109 ± 22 and 14N/15N = 330 ± 98 were obtained from HCN measurements, in agreement with previous values obtained from J = 4 → 3 data. Such ratios suggest that comet Hale-Bopp formed coevally with the solar system.

Original languageEnglish (US)
Pages (from-to)L67-L71
JournalAstrophysical Journal
Issue number1 PART 2
StatePublished - Dec 10 1999


  • Comets: individual (Hale-Bopp 1995 O1)
  • Molecular processes
  • Radio lines: solar system

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Ziurys, L. M., Savage, C., Brewster, M. A., Apponi, A. J., Pesch, T. C., & Wyckoff, S. (1999). Cyanide chemistry in comet Hale-Bopp (C/1995 O1). Astrophysical Journal, 527(1 PART 2), L67-L71.