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.