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Astron. Astrophys. 335, 765-768 (1998)

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Research Note

An attempt to detect the C2 intercombination transition lines in comet Hale-Bopp

P. Rousselot, C. Laffont, G. Moreels and J. Clairemidi

Observatoire de Besançon, BP 1615, F-25010 Besançon Cedex, France (philippe@obs-besancon.fr)

Received 13 February 1998 / Accepted 27 April 1998

Abstract

In this paper we report the first attempt to detect directly the intercombination transition lines of the C2 molecule in a comet. Indeed, these transitions play a key role in the C2 fluorescence process but had never been observed directly so far. We conducted an observational program with the Cerro Tololo Interamerican Observatory 4 m telescope, located in Chile, on September [FORMULA] and [FORMULA], 1997. The spectral range covered was 1.99 - 2.15 [FORMULA], in order to detect the emission lines of the [FORMULA] (3,0) band, that should be degraded to the blue with a bandhead located at 2.127 [FORMULA]. This band was chosen because of its expected brightness and its wavelength, corresponding to a good atmospheric transmission and a relatively low sky background. In this paper we present the theoretical calculation allowing to model the expected spectrum and the results obtained with our observational data. These results, unfortunately, cannot allow the detection of the expected emission lines. This is due to a too strong noise, generated by the sky background emission lines, that cannot be totally removed from the spectrum.

Key words: molecular processes – comets: general – comets: individual: C/1995 O1 (Hale-Bopp) – infrared: solar system

Send offprint requests to: P. Rousselot

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© European Southern Observatory (ESO) 1998

Online publication: June 18, 1998
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