Visible and Infrared Images of C/1999 S4 (LINEAR) during the Disruption of Its Nucleus

An analysis of the behavior of the dust coma of the Comet C/1999 S4 (LINEAR) from visible and infrared images acquired shortly before and after the disruption of the comet's nucleus is presented. During the predisruption phase, the overall dust production increased by a factor of 11 in two steps; an initial outburst occurred between July 18 and 19 and a second stronger one occurred between July 20 and 21. Postdisruption images obtained on July 26 and 27 suggest that most of the dust was released in the huge outburst produced during the disruption of the nucleus a few days before. The color of the dust coma did not show any measurable day-to-day variation and was also very uniform throughout the coma. The latter is an indication of the homogeneity of the dust component of the nucleus.