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  • Other Sources  (2)
  • 2015-2019
  • 1995-1999
  • 1985-1989  (2)
  • 1980-1984
  • 1986  (2)
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  • 2015-2019
  • 1995-1999
  • 1985-1989  (2)
  • 1980-1984
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  • 1
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    HCN production from Comet Halley (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Observations of the HCN J=1-0 rotational transition at 3.4 mm wavelength in comet P/Halley with a 14m antenna were obtained during 56 individual observing sessions between Nov. 1985 and May 1986. The HCN production rate is well correlated with the total visual magnitude of the comet, indicating that HCN follows the overall gas and dust production. However, comparison of HCN production to the total gas production of the comet indicates that it is a relatively minor consitiuent with 0.1% of the abundance of H2O. Spectra obtained by binning the HCN data with heliocentric distance show that the HCN line width, and thus the parent outflow velocity, increases with decreasing heliocentric distance, and that there is a tendency for the lines to be blue shifted as expected from the observed anisotropic outgassing from the nucleus. There is evidence of day-to-day time variability in the total HCN emission and variations in the HCN hyperfine ratios from their LTE values.
    Keywords: ASTROPHYSICS
    Type: ESA Proceedings of the 20th ESLAB Symposium on the Exploration of Halley's Comet. Volume 1: Plasma and Gas; p 577-581
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    HCN production from comet Halley (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The HCN J = 1-0 rotational transition at 3.4 mm wavelength has been detected and has been monitored in comet P/Halley during a total of 56 individual observing sessions between November 18, 1985 and May 11, 1986. The HCN spectra show significant daily variations in total intensity, but the average HCN production rate is well correlated with the visual magnitude of the comet over the range of heliocentric distance observed (between 0.59 and 1.8). Observations of the ratios of the F = 2-1 and F = 1-1 hyperfine components also exhibit significant daily variations but are, in the mean, consistent with the 5:3 ratio expected from the statistical weights of the hyperfine levels. The outflow velocity of the coma, deduced from the HCN linewidths, is 0.87 + or - 0.12 km/s, which is consistent with recent theoretical estimates as well as the measurements of the Giotto spacecraft.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 310; L55-L60
    Format: text
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