[vsnet-grb-info 28401] GRB 210722A: Nanshan/NEXT further optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30504
SUBJECT: GRB 210722A: Nanshan/NEXT further optical observations
DATE:    21/07/25 07:56:29 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu at nao.cas.cn>

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

We continued to observe the field of GRB 210722A (D'Avanzo et al., GCN 
30475) using the NEXT-0.6m telescope located at Nanshan, Xinjiang, 
China. We obtained 15x200 s frames in the Sloan r-band, starting at 
20:41:20 UT on 2021-07-24, i.e., 1.99 days after the burst.

The previously reported optical afterglow (e.g., D'Avanzo et al., GCN 
30475; Zhu et al., GCN 30476) is not detected in our stacked image, down 
to a limiting magnitude of r~21.0, calibrated with the nearby PanSTARRS 
field.