TITLE:   GCN CIRCULAR
NUMBER:  33708
SUBJECT: GRB 230427A: Gaoyazi/GOT optical upper limit
DATE:    23/04/28 15:42:19 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 230427A detected by Swift (Troja et al., GCN 33687) with the GOT-0.5m telescope located at Gaoyazi, Xinjiang, China. Observations started at 16:34:35 UT on 2023-04-27, i.e., 6.05 hr after the Swift/BAT trigger, 5 x 90 s and 10 x 120 s images were obtained in the Sloan r filter.

No optical source is detected in our stacked image at the UVOT position (Troja et al,. GCN 33687), down to a 3-sigma limiting magnitude r > 20.4 (AB) at 6.32 hr post-burst, calibrated with nearby PanSTARRS stars. The magnitude is not corrected for Galactic extinction.