[vsnet-grb-info 28402] GRB 210722A: continued Assy optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30505
SUBJECT: GRB 210722A: continued Assy optical observations
DATE:    21/07/25 08:13:48 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

V. Kim (FAI, Pulkovo Observatory), A. Pozanenko (IKI), N. Pankov (HSE, 
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 
21-07-24 (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, 30494; Kumar et al., GCN 30481; Butler et al., GCN 30484; 
Thoene et al., GCN 30487; Jelinek et al., GCN 30492; Fu et al., GCN  30504).

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)

2021-07-24 20:56:07   n/d       42*60    r'     21.3  0.2   21.7

The photometry is based on the nearby PS1 stars.

The photometry is  still compatible with the single power law of the 
afterglow light curve.