[vsnet-grb-info 28373] GRB 210722A: Nanshan/NEXT optical afterglow observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30476
SUBJECT: GRB 210722A: Nanshan/NEXT optical afterglow observations
DATE:    21/07/22 21:58:22 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu at nao.cas.cn>

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

We observed the field of GRB 210722A (D'Avanzo et al., GCN 30475) using 
the NEXT-0.6m telescope located at Nanshan, Xinjiang, China. We obtained 
a series of 40 s, 60 s, 90 s frames in the Sloan r-band, starting at 
20:56:45 UT on 2021-07-22, i.e., 123 s after the BAT trigger, among 
which part of the frames are useless due to the cloudy weather.

An uncatalogued optical transient is detected at the Swift/UVOT position 
(D'Avanzo et al., GCN 30475) with varying brightness, and thus confirms 
it as the optical afterglow of the burst. Preliminary analysis of the 
beginning photometry is as follows:

Tmid-T0(sec)  Mag    MagErr
143               14.33    0.01
361               13.94    0.01
452               14.01    0.01

All magnitudes are calibrated with the nearby PS1 field.