HCN SPECTROSCOPY OF COMET 73P/SCHWASSMANN-WACHMANN 3. A STUDY OF GAS EVOLUTION AND ITS LINK TO CN

In 2006 May, comet 73P/Schwassmann-Wachmann 3 experienced large outburst activity allowing us to study the gas production rate of fresh material released from the nucleus. We observed the comet in a coordinated campaign using millimeter and optical facilities at heliocentric distances between 0.966 and 1.033 AU. During this time, we had the opportunity to follow the post-outburst evolution of fragment B, which evidenced larger production rates in comparison to fragment C, the latter showing a rather stable gas production rate (Q HCN ∼2 x 1025 molecules s-1). In addition to the investigation of the gas evolution, we studied the possible role of HCN and dust as progenitors for the CN radical. From our joint observations on May 12, we observed a high correlation of CN with HCN and low correlation with the continuum emission (grains). Herewith, our study supports the view of HCN as a major source of CN, although the presence of other sources for cyanide cannot be fully ruled out.