TITLE:   GCN CIRCULAR
NUMBER:  30440
SUBJECT: GRB 210704A: Assy optical afterglow upper limit
DATE:    21/07/10 23:24:16 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

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

We observed GRB 210704A  (Ursi et al., GCN 30372; Berretta et al., GCN 
30375; Prasad et al., GCN 30378; D'Ai et al., GCN 30379; Malacaria et 
al., GCN 30380; Ridnaia et al., GCN 30388)  with AZT-20 telescope of 
Assy-Turgen observatory starting on 2021-07-08 (UT) 16:59:54. We do not 
detect the optical afterglow (Kim et al., GCN 30384; D'Avanzo et al., 
GCN 30385; Troja et al., GCN 30390; Kann et al., GCN 30391, 30401; Sun 
et al., GCN 30411; D'Avanzo et al., GCN 30432; Rastinejad  et al., GCN 
30433;  Watson et al., GCN 30436).

Preliminary photometry of the filed is following

Date       UT start  t-T0       Exp.   Filter  OT    Err.  UL(3sigma)
                     (mid, days)  (s)
2021-07-08 16:59:54  3.92014    77*60    r'    n/d   n/d   23.1

The photometry is based on the nearby PS1 stars.

Our photometry is consistent with observations of (D'Avanzo et al., GCN 
30432; Watson et al., GCN 30436).