[vsnet-grb-info 28375] GRB 210722A: Assy optical detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30478
SUBJECT: GRB 210722A: Assy optical detection
DATE:    21/07/22 22:49:40 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

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

We observed the field of  GRB 210722A  (D'Avanzo et al., GCN 30475) with 
AZT-20 telescope of Assy-Turgen observatory starting on 2021-07-22 (UT) 
21:42:07. We obtained 30 frames in r' - filter before a twilight.

We clearly detect the bright optical afterglow (D'Avanzo et al., GCN 
30475; Zhu et al., GCN 30476) in coordinates of 01:48:07.27 
-06:20:50.00 with accuracy of 0.1 arcsec in both coordinates. The 
coordinates are coincides with UVOT coordinates (D'Avanzo et al., GCN 30475)

Preliminary photometry of the optical afterglow in the first image of 60 
s exposure is following

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

2021-07-22 21:42:07 0.03293     1*60    r'      16.20 0.03  21.1


The photometry is based on the nearby PS1 stars.