EVOLUTION OF THE C-2 SPECTRUM IN COMETS P SCHAUMASSE AND P/TEMPEL-2/

The evolution of the emission spectrum of C-2 molecules (Swan bands (0 ,0) and (1,1)) was studied with two different methods in two different comets: P/Schaumasse and P/Tempel 2. Comet P/Schaumasse was observed in February 1993 in imagery mode with the 1.20-m telescope of the Obse rvatory of Haute-Provence (France). Three different interference filte rs were used, centered at 5125, 5160, and 5265 Angstrom. The data proc essing consisted of computing the ratio of the first two filters (the third one being used to subtract the solar continuum and the sky backg round). The images obtained show the evolution of the excitation tempe rature of the C-2 molecules. Comet P/Tempel 2 was observed in spectros copic mode in October-November 1988, with the 1.52-m Danish telescope of the European Southern Observatory (Chile). The results presented he re consist of a reanalysis of these observations, focused on the evolu tion of the (0,0) C-2 Swan band with cometocentric distance. In both c ases the C-2 spectrum reveals some important variations with cometocen tric distances up to about 10,000 km for P/Schaumasse and 20,000 km fo r P/Tempel 2 (which was located further from the Sun during the observ ations). These observations confirm the interest of modeling the C-2 f luorescence spectrum in comets by taking into account the states of th e molecules that are out of fluorescence equilibrium. (C) 1995 Academi c Press, Inc.