2 NEW LIGHT-ECHO STRUCTURES FROM SN-1987A AT LARGE DISTANCES

Observations since 1991 September 18 reveal two new (and possibly rela ted) light echo structures at 3140 and 3,240 lt-yr in the SN foregroun d. The details are presented herein. A forward-scattering light echo m odel is used to calculate the dust mass swept up by these echoes of 4. 0 M. and 1.7 M. as of 1993 May 1, and their extinction A(v) of 0.052 a nd 0.044 mag. The extinction calculated from light echo surface bright ness is shown to depend only weakly on dust models. We further specula te that these dust clouds, and the large-scale structures suggested by Bruhweiler et al. (1991), may be due to the same giant superbubble in the Large Magellanic Clouds, which was formed from the merger of seve ral smaller superbubbles.