TITLE:   GCN CIRCULAR
NUMBER:  30215
SUBJECT: GRB 210610B: CrAO/ZTSH optical observations and light curve
DATE:    21/06/11 23:23:01 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

N. Pankov (IKI, HSE), A. Pozanenko (IKI), V. Rumyantsev (CrAO),  S.
Belkin (IKI, HSE)  report on behalf of IKI GRB FuN:

We observed the GRB 210610B (Page  et al., GCN 30170) with ZTSH 2.6m
telescope of CrAO observatory starting on June 10 (UT) 20:19:24 
(Rumyantsev et al., GCNs 30175, 30178).  The optical afterglow  first 
reported by UVOT (Page  et al., GCN 30170) is clearly detected in each 
of a single image of 10 exposure in each of BVRI filters on June 10. 
Based on our observations on June 10 (B, R - filters) and June 11 
(Pankov et al., GCN 30213) we report the light curve (LC) of the 
afterglow which can be found in

http://grb.rssi.ru/GRB210610B/GRB210610B_LC.png

Initial phase of the LC from 0.02 days and up to 0.07 days can be 
approximated by a single power law with index of -0.9, and after that we 
observe plateau phase at least up to 0.18 days after trigger (see figure 
above).