TITLE:   GCN CIRCULAR
NUMBER:  22161
SUBJECT: GRB 171123A: Nanshan-1m optical upper limit
DATE:    17/11/24 15:38:53 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

Z.P. Zhu, H.X. Feng, D. Xu (NAOC), Z. Fan, W. Wang, J. Zheng, N. Song 
(NAOC), S.G. Ma, J. Liu (XAO), Y.D. Hu (IAA-CSIC) report

We observed the field of GRB 171123A (Evans et al., GCN 22148) using the 
1-m telescope located at Nanshan, Xinjiang, China. We obtained 3x120s, 
1x180s SDSS i-band and 1x120s r-band frames, starting at 21:12:40 UT on 
2017-11-23, i.e., 6.8 hr after the BAT trigger.

No optical source was detected in the stacked image at the XRT position 
(Goad et al., GCN 22150), down to a limiting magnitude of i~20.6 mag, at 
the median time of 6.92 hr post-burst, calibrated with the SDSS field.