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L.M. Woodney (Univ. Central Florida), Y.R. Fernandez, T.C Owen (IfA, Univ Hawaii)
We present the first measurement of HCN emission in Comet 2P/Encke. The comet was observed during its close approach to Earth over UT 2003 Nov 9 to 11 with the James Clerk Maxwell Telescope atop Mauna Kea, Hawaii. The J=4arrow 3 transition at 354.506 GHz was observed to have an integrated line strength of 0.057 ± 0.011 K km/s. Using a Haser model we derive an HCN production rate of Q \approx 1\times1024 molecules/s. The production rate of CN near this time was Q \approx 5\times1024 molecules/s (Schleicher, priv. comm.). This implies HCN dissociation contributes only a small fraction of Encke's comatic CN. This fraction is smaller than that seen in the long-period comets which have a discrepancy between HCN and CN and smaller than that seen in the only other Jupiter-family comet with an HCN detection, 19P/Borrelly. CN must have another parent in addition to HCN in 2P/Encke. We also present upper limits for both the integrated line strength of the CO J=3arrow 2 transition at 345.796 GHz and the 850-\mum continuum emission.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.