[vsnet-grb-info 20050] GRB 171120A: Xinglong-2.16m optical upper limit

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22145
SUBJECT: GRB 171120A: Xinglong-2.16m optical upper limit
DATE:    17/11/22 04:24:59 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu at nao.cas.cn>

Z.P. Zhu, H.X. Feng, D. Xu (NAOC), Y. Zhao, F. Xiao (NAOC), S.B. Qian 
(YNAO), Y.D. Hu (IAA-CSIC) report

We observed the field of GRB 171120A (Tohuvavohu et al., GCN 22133) 
using the 2.16-m telescope located at Xinglong, Hebei, China, equipped 
with BFOSC. We obtained 1x600s and 2x900s R-band frames, starting at 
18:54:02 UT on 2017-11-20, i.e., 5.57 hr after the BAT trigger.

No optical source was detected in the stacked image at the XRT position 
(Evens et al., GCN 22135), down to the limiting magnitude of R~21.5 mag 
at the median time of 5.95 hr post-burst, calibrated with the SDSS field.