TITLE:   GCN CIRCULAR
NUMBER:  31823
SUBJECT: GRB 220403B: Nanshan/NEXT optical afterglow power-law decay
DATE:    22/04/03 23:17:19 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

Z.P. Zhu (NAOC,HUST), S.Q. Jiang, X. Liu, S.Y. Fu, D. Xu (NAOC), X. Gao 
(Urumqi No.1 Senior High School), J.Z. Liu (XAO) report:

We observed the field of GRB 220403B detected by Swift (Klingler et al., 
GCN 31820) using the NEXT-0.6m telescope located at Nanshan, Xinjiang, 
China. Observations started at 21:10:31 UT on 2022-04-03 (i.e., 27.8 min 
after the BAT trigger), and a series of 300 s frames were obtained in 
the Sloan r-filters.

The optical afterglow (Klingler et al., GCN 31820) is clearly detected 
in each of our images. The preliminary photometric analysis shows that 
the afterglow decays from r ~ 19.04 to r ~ 19.64 in 47 minutes, with a 
decay index of \alpha ~ 0.6 (F_t ~ t^-\alpha), calibrated the nearby PS1 
stars.

Our measurement is consistent with that in other reports (Jelinek et 
al., GCN 31821; Nicuesa Guelbenzu et al., GCN 31822).