Z.P. Zhu (NAOC, HUST), S.Y. Fu, M. Zhang, X. Liu, D. Xu (NAOC), X. Gao (Urumqi
No.1 Senior High School), J.Z. Liu (XAO) report:
We observed the field of GRB 201223A (Gropp et al., GCN 29158) using the
NEXT-0.6m optical telescope located at Nanshan, Xinjiang, China.
Observations automatically started at 18:01:14 UT on 2020-12-23, i.e.,
168 s after the BAT trigger. We obtained a series of 2x40s, 4x60s and
12x90s frames in the Sloan r-filter, and observations are ongoing.
An uncatalogued decaying optical transient is detected at the Swift/UVOT
position (Gropp et al., GCN 29158), which is thus concluded to be the
optical afterglow of burst. The afterglow has r = 15.67 +/- 0.01 mag in
our first image, calibrated with nearby PS1 stars.
[GCN OPS NOTE(24Dec2020) Per author's request, M. Zhang was added
to the author list.]