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N.H. Samarasinha (NOAO/PSI), D.G. Schleicher (Lowell Observatory), L.M. Woodney (University of Central Florida)
During its close perigee passage, comet Hyakutake (C/1996 B2) showed coma structures in both continuum (dust) and in emission (gas) narrowband images. Both the primary jet as well as the much fainter secondary jet in the continuum images which were observed as a function of the rapidly changing observing geometry were used by Schleicher and Woodney (2003, Icarus, 162, 190-213) to derive a detailed activity model for the nucleus. In present work, we use this model together with the CN images of Hyakutake to characterize the CN jet features seen in the coma. Coma simulations using Monte Carlo codes indicate that the nuclear active regions identified in the Schleicher and Woodney model can satisfactorily reproduce the CN jets observed. The full-spiral CN jets, which are unlike the dust jets with a high degree of sunward side dominance, have measured bulk outflow velocities of the order of 0.6-0.7 km/s between 2000-8000 km from the nucleus (i.e., approximately a factor two larger outflow velocities than the corresponding dust jets). The pair of CN jets are more comparable in brightness to each other than the corresponding dust jets are to each other.
The analysis so far indicates that the "effective" CN excess velocity in its precursor frame is of the order of 0.3 km/s. This excess velocity is presumed to be a reduction from its "real" value (i.e., if one assumes HCN is the precursor) due to the ambient collisional environment in which the CN jets are located. We will discuss how collisional environment and the projection effects would have affected the gross morphology as well as the measured properties of the CN jets. In addition, we will compare and contrast the properties of the dust and CN jets and in particular, their relative strengths, diurnal behavior, and the bulk outflow velocities.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.