TITLE: GCN CIRCULAR NUMBER: 30712 SUBJECT: GRB 210822A: TSHAO optical observation DATE: 21/08/25 09:49:39 GMT FROM: Alexei Pozanenko at IKI, Moscow apozanen@iki.rssi.ru

S. Belkin (IKI), A. Kusakin (FAP), I. Reva (FAP), Pozanenko (IKI), N. Pankov (HSE), V. Kim (FAP) report on behalf of GRB-IKI-FuN:

We observed GRB 210822A (Page et al., GCN 30677; Wang et al., GCN 30678; Prasad et al., GCN 30693; Frederiks et al., GCN 30694) with Zeiss-1000 telescope of Tien Shan Astronomical Observatory on Aug. 22 (UT) 15:48:55 -- 18:48:47. We obtained series with 20 and 30 sec exposition in R-filter.

The optical afterglow (Page et al., GCN 30677; Zheng et al., GCN 30679; Butler et al., GCN 30680; Fu et al., GCN 30684; Zhu et al., GCN 30692; Romanov et al., GCN 30701; Guelbenzu et al., GCN 30703; Siegel et al., GCN 30710) at redshift z = 1.736 (Zhu et al., GCN 30692) is detected in stacked images. Preliminary photometry of the afterglow in a stacked image of the second series is following.

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

2021-08-22 17:26:41 0.36184 R 196*20 18.63 0.03 21.0

The photometry is based on nearby USNO-B1.0 stars.

USNO-B1.0 RA Dec R2 20:18:06.64416 +05:17:24.1404 12.33 20:17:59.55288 +05:18:19.5912 13.05