31st Annual Meeting of the DPS, October 1999
Session 32. Comet Comae I
Contributed Oral Parallel Session, Wednesday, October 13, 1999, 8:30-10:00am, Sala Plenaria

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[32.05] Infrared Investigation of Parent Molecules in Comet C/Lee (1999~H1)

H.A. Weaver (JHU), J.K. Davies, T. Kerr (JAC), W. Vacca, N. Biver (IfA/UH), D. Bockel\'ee-Morvan, J. Crovisier (Meudon), T.Y. Brooke (JPL), G. Chin (GSFC), S.J. Kim (Kyunghee)

Infrared observations of C/Lee were made preperihelion using CSHELL at the IRTF and CGS4 at the UKIRT. Using high spectral resolution (\lambda/\delta\lambda ~10,000) CSHELL data taken on UT May~20.3 (r=1.22~AU, \Delta=0.86~AU), we detected the rQ2 (F=5.9 \times 10^{-18} W m^{-2} in a 2'' \times 4'' aperture) and rQ3 (F=8.7 \times 10^{-18} W m^{-2}) subbands of the C2H6 \nu7 band near 3.35~\mum, from which we estimate a production rate of \sim 0.7-1.4 \times 10^{27} s^{-1} for T_{rot} = 50 K. The CH4 P2 lines were possibly detected at the 3\sigma level (F=1.9 \times 10^{-18} W m^{-2}) in the same spectral region, and we derive a production rate of \sim 4.5 \times 10^{26} s^{-1} for T_{rot} = 50 K. Moderate resolution (\lambda/\delta\lambda ~1000-7000) CGS4 spectra of C/Lee were taken during UT 20-29 May (1.10 \leq r \leq 1.24 AU, 0.84 \leq \Delta \leq 1.02 AU) and covered the wavelength range from 2.94 to 4.75~\mum. We detected strong emissions in the C-H stretch region near 3.4~\mum and a broad emission feature centered near 3.27~\mum that may be associated with PAHs. Assuming that all of the flux in the emission feature centered near 3.51~\mum (F=4.0 \times 10^{-17} W m^{-2} in a 0.\!''61 \times 1.\!''83 aperture) is due to fluorescence from CH3OH, we derive a preliminary production rate of \sim 2 \times 10^{27} s^{-1}. No day-to-day temporal variability was observed at the 20% level during the entire period of CGS4 observations. Post-perihelion CSHELL and CGS4 observations of C/Lee are planned for the first week of September 1999, and we hope to present preliminary results from those.

We gratefully acknowledge financial support for this work from NASA through grant NAG5-7186 from the Planetary Astronomy Program and through grant 96-07-02-03-01-3 from the Korean Science and Engineering Foundation.

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