Observations of submillimeter lines of CH3OH, HCN, and H2CO in comet P/Swift-Tuttle with the James Clerk Maxwell Telescope

Details Observations of submillimeter lines of CH3OH, HCN, and H2CO in comet P/Swift-Tuttle with the James Clerk Maxwell Telescope Observations of submillimeter lines of CH3OH, HCN, and H2CO in comet P/Swift-Tuttle with the James Clerk Maxwell Telescope

Aug 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994p%26ss...42..655b&link_type=abstract

Planetary and Space Science (ISSN 0032-0633), vol. 42, no. 8, p. 655-662

Computer Science

18

Abundance, Comets, Density Distribution, Outgassing, Rotational States, Stellar Atmospheres, Stellar Models, Molecular Excitation, Spectroscopy

Scientific paper

We present submillimeter molecular line observations of comet P/Swift-Tuttle (1992t = 1992 XXVIII) which were undertaken on 7 and 8 December 1992 with the James Clerk Maxwell Telescope (JCMT). Three molecules were detected: (1) HCN through its J (4-3) rotational line at 354.505 GHz; (2) H2CO through its 515 - 1414 ortho line at 351.769 GHz and (3) CH3OH through several of its J (7-6) transitions at 338 GHz and one line at 341 GHz. These lines are blueshifted with respect to the comet rest velocity, which is indicative of preferential outgassing towards the Sun. The relative intensities of the CH3OH rotational lines show that the population distribution can be described by a rotational temperature of 45 +/- 7K, although deviations from thermal equilibrium are present. The comparison with an out-of-equilibrium model suggests that the collisional region where thermalization occurs is larger than is expected in an isotropic coma where neutral-neutral collisions prevail. From these observations, we derive production rates of Q(HCN) = 1.3 x 1027/s, QH2CO) = 5 x 1027/s and Q(CH3OH) = 2 x 1028/s, assuming direct release from the nucleus and isotropic sublimation. This corresponds to molecular abundances with respect to water of 0.3, 1 and 4%, for HCN, H2CO and CH3OH, respectively.

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