[vsnet-grb-info 19770] GRB 170903A: Nanshan optical upper limit

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21795
SUBJECT: GRB 170903A: Nanshan optical upper limit
DATE:    17/09/03 15:01:49 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu at nao.cas.cn>

H.X. Feng, D. Xu, Z.P. Zhu (NAOC), S.G. Ma, T.Z. Yang, J.H. Liu, P. 
Zong, H.B. Niu, J.Z. Liu,  A. Esamdin, L. Ma (all XAO), Y.D. Hu 
(IAA-CSIC), Y. Qing (Geneva Observatory) report:

We observed the field of GRB 170903A (Markwardt et al., GCN 21793) using 
the 1m telescope located at Nanshan, Xinjiang, China. We obtained 3x180s 
R-band frames, starting at 14:08:09 UT on 2017-09-03, i.e., 1.317 hr 
after the burst.

No optical source is detected at the XRT position (Campana et al., GCN 
21794) in the stacked image, down to a limiting magnitude of m(R)~21.3, 
calibrated with the nearby SDSS field.