TITLE: GCN CIRCULAR NUMBER: 4123 SUBJECT: GRB 051021 : optical afterglow observation at Lulin DATE: 05/10/21 19:19:48 GMT FROM: Kuiyun Huang at IANCU GRB 051021 : optical afterglow observation at Lulin H.H. Hsieh (IfAUH), M.S. Chang, K.Y. Huang, W.H. Ip (NCU), Y. Urata (RIKEN), Y. Qiu (BAO) on behalf of the East Asian collaboration report: The R-band observations of GRB 051021 (Yoshida et al., GCN 4116) were taken by Lulin 1-m telescope, Taiwan. The optical afterglow reported by Fox et al.(GCN 4120) was detected clearly in our R-band images. Compared with USNOB stars, the R band magnitude of afterglow is about 19.8 at 15.859 UT (~ 2.48 hrs after the burst). Further observations are on going. This message may be cited.