In the GOES plot shown above, we notice four C6-9 flares around 15-Apr-98. They all came from the same region, AR 8203. The first one, in particular, was likely to be responsible for the CME observed by LASCO C2 on the NNW limb. The Yohkoh coverage for these flares was not very good. The expanded GOES time profiles are shown below (click to enlarge).
But we were able to trace the region back to its birth. The following movie shows that AR 8203 emerged on 14-Apr-98. For several hours, it looked like an XBP. After the four C-class flares, the region apparently stopped growing and started being fragmented. Note that the short time span between the birth and the major flare activity. This may mean the flares exhausted most of the free energy of the AR which was accumulated for one day.