TITLE: GCN CIRCULAR NUMBER: 12377 SUBJECT: GRB 110921A : TNT optical counterpart candidate DATE: 11/09/21 16:30:38 GMT FROM: L.P. Xin at NAOC L.P. Xin, J.Y. Wei, Y. L. Qiu, J. Wang, J.S. Deng, C. Wu, X. H. Han on behalf of EAFON report: We began to observe GRB 110921A (Baumgartner et al., GCN 12373) with Xinglong TNT telescope at 13:59:40 (UT), about 8 min after the burst. 25 White-band images and a series of R-band data were obtained. A new source was detected in the combined white band image within the errorbox of XRT position. The brightness of this new source is estimated to be about 20.2 mag derived from USNO B1.0 R2mag. We propose that this source is the candidate of optical counterpart of GRB 110921A. More deep observations are needed to confirm this. This message may be cited. For more information about Xinglong GRBs Follow-up observations, please visit the website: http://www.xinglong-naoc.org:8080/grb/index.html