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Astron. Astrophys. 324, 357-365 (1997)

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5. Summary

Assuming a fairly narrow distribution of velocities for [FORMULA] ballistic trajectories, we can explain several of the features observed in our H lightcurve as well as in published lightcurves for the L impact. We can also explain some of the features in the near-infrared lightcurves. In particular, the time of the first detection of the plume at visible wavelengths is accounted for by 9 [FORMULA] 1 km/s ejecta, which comprise most of the plume and the 11-km/s ejecta are responsible for the second maximum in the CCD lightcurves. The 9-km/s ejecta are also responsible for the beginning of the second precursor seen at near-infrared wavelengths and for the main peak. The first maximum in CCD lightcurves is at its widest phase in height and the maximum amount of material is exposed to sunlight. A fraction of the plume, the portion with velocities lower than 9 km/s, is responsible for the minimum when it disappears from direct solar illumination in the descending part of the trajectory. The CCD emission in the second maximum originates at pressures 25 [FORMULA] mbar and 35 [FORMULA] mbar for the L and H impacts, respectively. The near-infrared peak occurs before the second maximum in the CCD lightcurves.

We note that further elucidation of these processes will be possible when additional synoptic observations of the H and L impacts at shorter wavelengths are considered. This will give us a better description of the thermal behavior of the ejecta from its continuum emission. Ultimately, the most quantitative progress will be made by extending these calculations to a spatially inhomogenous thermophysical model for the ejecta which is coupled with appropriate radiative transfer calculations. These can then be compared with Galileo and earth-based observations at a variety of wavelengths.

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© European Southern Observatory (ESO) 1997

Online publication: May 26, 1998