[vsnet-grb-info 27015] GRB 201221D: Nanshan/NEXT early optical upper limit

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29118
SUBJECT: GRB 201221D: Nanshan/NEXT early optical upper limit
DATE:    20/12/22 01:38:32 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu at nao.cas.cn>

D. Xu (NAOC), Z.P. Zhu (NAOC, HUST), S.Y. Fu, X. Liu (NAOC), X. Gao 
(Urumqi No.1 Senior High School), J.Z. Liu (XAO) report:

We observed the field of GRB 201221D (Page et al., GCN 29112) using the 
NEXT-0.6m optical telescope located at Nanshan, Xinjiang, China. 
Observations automatically started at 23:07:39 UT on 2020-12-21, i.e., 
65 s after the BAT trigger. We obtained 3x40s, 4x60s and 12x90s frames 
in the Sloan r-filter.

No optical source is detected in our stacked image at the XRT enhanced 
position (Evans et al., GCN 29113), down to a upper limit of r~21.3, 
calibrated with the nearby PanSTARRS field.