[vsnet-grb-info 28385] GRB 210722A: Kitab optical observations, light curve

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30488
SUBJECT: GRB 210722A: Kitab optical observations, light curve
DATE:    21/07/23 17:59:25 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

N. Pankov (IKI, HSE), A. Zhornichenko (KIAM),  A. Pozanenko (IKI), V. 
Agletdinov (KIAM),  M. Krugov (FAI), V. Kim (FAI), S. Belkin (IKI), Sh. 
Ehgamberdiev (UBAI) report on behalf of IKI-GRB-FuN:

We observed the field of  GRB 210722A  (D'Avanzo et al., GCN 30475) with 
Kitab-ISON RC-36  telescope in Clear filter.  Observation started on 
July, 22  (UT) 21:31:44 and ended on July, 22  (UT) 23:20:06. We clearly 
detect the bright optical afterglow (D'Avanzo et al., GCN  30475; Zhu et 
al., GCN 30476; Pankov et al., GCN 30478; Lipunov  et al., GCN  30480; 
Kumar et al., GCN  30481; Siegel et al., GCN  30421; Butler et al., GCN 
  30484).
Preliminary photometry of the first and latest combined images are following


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

2021-07-22  21:31:44 0.02572   5*60  CR      16.00  0.15   18.4
2021-07-22  23:13:54 0.09667   7*60  CR      17.33  0.12   19.0

The photometry is based on nearby USNO-B1.0 stars, R2 magnitude.
USNO-B1.0_id R2
USNO_B10-0836-00016699
USNO_B10-0836-00016715

We approximate the light curve by single PL model with power law index 
of -1.1 which is corroborating with PL index reported by Kumar et al. 
(GCN  30481).  The light curve of our observations in Assy (Pankov et 
al., GCN 30478) and Kitab observatory can be found at

http://grb.rssi.ru/GRB210722A/GRB210722A_LC.jpeg