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Long term evolution of the outgassing of Comet Hale-Bopp from radio observations

N. Biver1, D. Bockelée-Morvan2, P. Colom2, J. Crovisier2, B. Germain2,E. Lellouch2, J.K. Davies3, W.R.F. Dent3, R. Moreno2, G. Paubert4, J. Wink5, D. Despois6, D.C. Lis7, D. Mehringer7, D. Benford7, M. Gardner7, T.G. Phillips7, M. Gunnarsson8, H. Rickman8, A. Winnberg9,P. Bergman9, L.E.B. Johansson9, and H. Rauer tex2html_wrap_inline821 IfA, University of Hawaii, U.S.A.
tex2html_wrap_inline829 Observatoire de Paris-Meudon, France
tex2html_wrap_inline895 Royal Observatory, Edinburgh, U.K. and Joint Astronomy Centre, Hawaii, U.S.A.
tex2html_wrap_inline1069 Institut de Radio Astronomie Millimétrique, Grenoble, France
tex2html_wrap_inline1071 Observatoire de Bordeaux, France
tex2html_wrap_inline1073 Caltech, California, U.S.A
tex2html_wrap_inline1075 Uppsala Astronomiska Observatorium, Sweden
tex2html_wrap_inline1077 Onsala Space Observatory, Sweden
tex2html_wrap_inline1079 DLR, Institut für Planetenerkundung, Berlin, Germany
Abstract: C/1995 O1 (Hale-Bopp) has been observed on a regular basis since August 1995 at millimetre and submillimetre wavelengths using IRAM, JCMT, CSO and SEST radio telescopes. The production rates of eight molecular species (CO, HCN, CH tex2html_wrap_inline795 OH, H tex2html_wrap_inline803 CO, H tex2html_wrap_inline803 S, CS, CH tex2html_wrap_inline795 CN, HNC) have been monitored as a function of heliocentric distance ( tex2html_wrap_inline1089 ) from 7 AU pre-perihelion to 4 AU post-perihelion (Fig. 4). As comet Hale-Bopp approached and receded from the Sun, these species displayed different behaviours. Far from the Sun, the most volatile species were found in general relatively more abundant in the coma. In comparison to other species, HNC, H tex2html_wrap_inline803 CO and CS showed a much steeper increase of the production rate with decreasing tex2html_wrap_inline1089 . Less than 1.5 AU from the Sun, the relative abundances were fairly stable and approached those found in other comets near 1 AU.

The kinetic temperature of the coma, estimated from the relative intensities of the CH tex2html_wrap_inline795 OH and CO lines, increased with decreasing tex2html_wrap_inline1089 , from about 10 K at 7 AU to 110 K around perihelion. The expansion velocity of the gaseous species, derived from the line shapes, also increased with a law close to tex2html_wrap_inline1099 .



Figure: Production rates of the different molecular species as functions of heliocentric distance

To appear in Proceedings of the First International Hale-Bopp Conference, Puerto De La Cruz (Tenerife), Spain, Feb. 2-5, 1998.

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Next: New Preprints Up: Scientific results Previous: A search for (HO)