TITLE:   GCN CIRCULAR
NUMBER:  29270
SUBJECT: GRB 210102B: Assy optical afterglow identification
DATE:    21/01/06 15:55:15 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

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

We continued observations of  XRT candidate (Burrows  et al., GCN 29230) 
of MAXI GRB 210102B (Guo et al., GCN 29223) with AZT-20 telescope of 
Assy-Turgen observatory starting on  Jan. 05 (UT) 13:00:53, i.e.  ~3.2 
days after trigger.  At the place of the only one of XRT candidate 
(Burrows  et al., GCN 29230)  we do not detect the optical object found 
early (Pozanenko et al., GCN 29240).
Preliminary photometry of the field is following

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

2021-01-05 13:00:53   3.20177   r'(AB) 76*60  n/d n/d   23.1

The photometry is based on the stars of PanSTARRS-PS1
RA DEC r'
23:35:20.67802 -21:04:16.4688 19.656
23:35:47.99017 -21:11:53.6544 17.807

We confirm the optical object reported in GCN 29240 as an afterglow of 
GRB 210102B.