TITLE:   GCN CIRCULAR
NUMBER:  30494
SUBJECT: GRB 210722A: continued Assy optical observations
DATE:    21/07/24 12:10:35 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

N. Pankov (HSE, IKI), V. Kim (FAI, Pulkovo Observatory), A. Pozanenko 
(IKI),  M. Krugov (FAI),  S. Belkin (IKI) report on behalf of GRB IKI FuN:

We continue observations of of the field of GRB 210722A  (D'Avanzo et 
al., GCN 30475;  Page et al., GCN 30483; Barthelmy et al. GCN 30489; 
Wood et al., GCN30490)  with AZT-20 telescope of Assy-Turgen 
observatory. We obtained several frames  in r' - filter starting on 
21-07-23 (UT) 21:34:39. We clearly detect the bright optical afterglow 
(D'Avanzo et al., GCN 30475; Zhu et al., GCN 30476; Pankov et al., GCN 
30478 & 30488; Kumar et al., GCN 30481; Butler et al., GCN 30484; 
Thoene et al., GCN 30487; Jelinek et al., GCN 30492).

Preliminary photometry of the afterglow in the stacked image  is following

Date       UT start  t-T0       Exp.    Filter  OT    Err.  UL(3sigma)
                     (mid, days)  (s)             (AB)

2021-07-23 21:34:39 1.03677    26*60    r'      20.37 0.07  22.5

The photometry is based on the nearby PS1 stars.

The light curve can still be approximated by a single power law with a 
an index of -1.1.