TITLE:   GCN CIRCULAR
NUMBER:  33664
SUBJECT: GRB 230420A: Gaoyazi/GOT optical upper limit
DATE:    23/04/21 09:07:17 GMT
FROM:    Dong Xu at NAOC/CAS <dxu@nao.cas.cn>

S.Y. Fu,  S.Q. Jiang, X. Liu, T.H. Lu, D Xu (NAOC), Z.P. Zhu (NAOC, HUST), S.W. Luo, M.M. Yang, Z. K. Feng (GYZO, NAOC) report

We observed the field of GRB 230420A detected by Swift (Klingler et al., GCN 33658) with the 0.5-meter Gaoyazi Optical Telescope (GOT) located at Gaoyazi, Xinjiang, China. Observations started at 17:23:51 UT on 2023-04-20, i.e., 0.30 days after the Swift/BAT trigger, and 20 x 180 s images were obtained in the Sloan r filter.

No optical source is detected in our stacked image at the enhanced XRT position (Osborne et al,. GCN 33661), down to a limiting (3-sigma) magnitude of r > 21.6 at 0.32 days post-burst, calibrated with nearby PanSTARRS stars.