TITLE:   GCN CIRCULAR
NUMBER:  29884
SUBJECT: GRB 210420B: Correction to AST3-3 YaoAn magnitude
DATE:    21/04/22 18:48:15 GMT
FROM:    Tianrui Sun at Purple Mountain Obs,CAS  <trsun@pmo.ac.cn>

There was a program error to the AST3-3 YaoAn observation:
The two magnitudes reported by Tianrui Sun et al.(GCNC 29848) for GRB 210420B contain an error.
Thus, the correct description should be: 
The detected candidate source in g-band was 18.6 mag +/- 0.06 at 2021-04-20T20:07:30.596 and 19.13 mag +/- 0.1 mag at 2021-04-20T21:42:43.897.