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[23.04] OH Vibrational Prompt Emission and Water Hot-Band Fluorescent Emission in C/2000 WM1 (LINEAR)

B. P. Bonev (The Univ. of Toledo & NASA's GSFC), M. J. Mumma (NASA's GSFC), N. Dello Russo (The Catholic Univ. of America & NASA's GSFC), M. A. DiSanti (NASA's GSFC), E. L. Gibb (Univ. of Notre Dame), K. Magee-Sauer (Rowan Univ.), H. A. Weaver (Applied Physics Laboratory - JHU), G. Chin (NASA's GSFC)

Two methods for deriving cometary water production rates from ground-based high-resolution near-infrared spectra have now been developed. The water molecule can be directly sampled through "hot-band" fluorescent emission near 2.0, 2.9, 4.6, and 5.0 \mum [1]. Knowledge of the H₂O rotational temperature and ortho-to-para ratio is needed to fully constrain its production rate via this method. More recently, vibrational prompt emission from OH has also been used as a proxy for water production. This method depends on the accuracy of the OH emission efficiencies derived from simultaneous observations of H₂O and OH in comets C/1999 H1 (Lee) and C/2001 A2 (Linear) [2].

We report water production rates for a third comet (C/2000 WM1) based on independent analyses of H₂O hot-band lines near 2.9 \mum and of OH prompt emission lines near 3046 cm^-1, observed with NIRSPEC at the W. M. Keck Observatory. This comparison further reveals the capabilities and potential limitations of the two methods, while placing a special emphasis on the newer OH-based method.

This work was supported by grants to M. J. Mumma (RTOP 344-32-30-07) and to H. A. Weaver and G. Chin (NAG5-12230) under NASA's Planetary Astronomy Program, and to N. Dello Russo (NAG5-10795) under NASA's Planetary Atmospheres Program.

[1] Dello Russo et al. 2002, JGR, 107 (E11) 5095. [2] Bonev et al. 2004, ApJ, in press.

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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.