TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5608 SUBJECT: GRB060923C: AROMA optical obsevation DATE: 06/09/25 12:45:25 GMT FROM: Atsumasa Yoshida at Aoyama Gakuin U T.Uehara, I.Takahashi, K.Yoshida, A.Kobayashi, D.Oyamada, Y.E.Nakagawa, S.Sugita, K.Yamaoka, A.Yoshida (AGU) report: We have observed the feild of GRB060923C (Stamatikos et al. GCN 5591) from 13:35:46 (UT) with 0.3m AROMA robotic telescope with R-band filter at Aoyama Gakuin University. Although the weather condition was not good, we have taken 60 frames of image with 20s exposure each. The photometric calibration was made by first 5 and every 20 frames by comparing with USNO A2.0 stars in the same field. No new source was found. The 3 sigma limiting magnitude of each combined image is as below. number mean time since limiting magnitude of frames time (UT) GRB (s) in R (3 sigma) ======================================================================== 5 13:36:39 217 15.4 20 13:40:20 436 15.8 20 13:54:06 1264 16.8 20 14:10:26 2244 17.5