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A. A. Simon (New Mexico State University)
In early 1998 it was reported by amateur observers, and confirmed by IRTF and Pic-du-Midi observations, that two of Jupiter's classical White Ovals, BC and DE, had merged (IAU circ. #6942). 5 orbits of Hubble Space Telescope Target of Opportunity WFPC2 observations were granted for June 3, 1998 and July 16, 1998 to observe the post-merger state of the oval region. Preliminary analysis of the remaining ovals over a range of incident and emergent light angles sets limits on the morphology, rotational velocities and translation rates and characterizes the surrounding zonal structure.
In the context of historical observations, the ovals appear to be behaving in a manner similar to that seen whenever ovals have interacted. There has been an acceleration of the new oval, which is now gradually decelerating as it experiences drag from its surroundings. Qualitatively, the new oval's morphology and structure in a wide range of filters (410 to 953 nm) is similar to the pre-merger structure of BC, indicating that the new oval has a character similar to that of the other White Ovals.
The authors wish to acknowledge the observers of the ALPO and the IJW for their diligent efforts in obtaining transit times and images of these events. These results are based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract No. NAS5-26555.