TITLE:   GCN CIRCULAR
NUMBER:  29417
SUBJECT: GRB 210204A (ZTF21aagwbjr/AT2021buv): Mondy and AbAO optical observations
DATE:    21/02/07 16:34:13 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), R. Ya. Inasaridze 
(AbAO), N. Pankov (HSE) report  on behalf of GRB IKI FuN:

We observed the ZTF21aagwbjr/AT2021buv transient (Kool  et al., GCN 
29405) at  the redshift of 1.466 (Izzo et al., GCN 29411) which is most 
probably is an afterglow (Kennea et al., GCN 29413; Teja  et al., GCN 
29414) of  GRB 210204A (Fermi GBM team, GCN 29390; Li et al., GCN 29392; 
Hurley et al., GCN 29408; Waratkar et al., GCN 29410;  Frederiks et al., 
GCN 29415). Images in R-filter were taken in AZT-33IK telescope of Sayan 
observatory (Mondy) and AS-32 telescope of Abastumani observatory (AbAO).

Preliminary photometry of the optical transient in a combined image is 
following

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

2021-02-06 12:33:10  2.26579  R      38*60 19.94 0.09  21.7  AZT-33IK
2021-02-06 16:50:17  2.44748  R      47*60 20.1  0.4   20.1  AS-32

The photometry is based on the nearby USNO-B1.0 stars.
USNO-B1.0_id R2
1014-0149033 15.43
1014-0149115 17.00