TITLE: GCN CIRCULAR NUMBER: 16261 SUBJECT: GRB 140512A: Xinglong TNT optical observation DATE: 14/05/13 16:25:20 GMT FROM: L.P. Xin at NAOC L. P. Xin, X. F. Wang, J. Y. Wei, Y. L. Qiu, J. S. Deng, J. Wang, X. H. Han and C. Wu on behalf of EAFON report: We began to observe GRB 140512A (Pagani et al., GCN 16429) with Xinglong 0.8-m TNT telescope at 19:33:54 (UT) , 126 sec after the burst. The optical counterpart (Pagani et al., GCN 16429) was clearly detected in our white and R band images. A preliminary analysis shows that the brightness of the OT was fading from 13.0 mag to 17.0 mag, calibrated by nearby USNO B1.0 R2mag, during our observation epoch, with an index of 1.54 after fitting by a single power law. The message may be cited.