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The Infrared Spectrum of Comet Hale-Bopp
J. Crovisier1
- K. Leech 2
- D. Bockelée-Morvan 1
- T.Y. Brooke 3
-
M.S. Hanner 3
- B. Altieri 2
- H.U. Keller 4
- E. Lellouch 1
1 Observatoire de Paris-Meudon, F-92195 Meudon, France
2 ISO Science Operations Centre, Astrophysics Division of ESA,
Villafranca, Spain
3 Jet Propulsion Laboratory, Pasadena, USA
4 MPI für Aeronomie, Katlenburg-Lindau, Germany
Spectra of comet C/1995 O1 (Hale-Bopp) were observed at medium
resolution with PHT-S and at high resolution with the long- and
short-wavelength spectrometers of the Infrared Space Observatory on
September-October 1996, when the comet was at about 3 AU from the Sun.
For the first time, a high-resolution spectrum of a comet covering the
entire 2.4 to 200 
m spectral range was obtained.
The vibrational bands of water, carbon dioxide and carbon monoxide are
detected in emission with PHT-S, as expected from molecular
fluorescence models. Relative production rates of 100:22:70 are
derived for H
O:CO:CO. HO is observed at high spectral
resolution in the 
group of bands around 2.7 m and the
group around 6 m with SWS, and in a couple of rotational
lines near 180 m with LWS. The rovibrational lines of the
band are observed with a high signal-to-noise ratio. This
allows accurate determinations of the water rotational temperature and
of its ortho-to-para ratio.
Longward of 6 m, the spectrum is dominated by dust thermal continuum
emission, upon which broad emission features are superimposed. The wavelengths
of the emission peaks correspond to those of Mg-rich crystalline olivine
(forsterite).
Highlights of these results were briefly reported in Crovisier et al. (1997). We will present the latest developments of their analysis.
Postscript version