[vsnet-grb-info 27135] GRB 210104A: Assy optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29238
SUBJECT: GRB 210104A: Assy optical observations
DATE:    21/01/04 14:22:05 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

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

We observed the GRB 210104A (Fermi GBM team, GCN 29232; Troja et al., 
GCN  29233) with AZT-20 telescope of Assy-Turgen observatory starting on 
  Jan. 04 (UT) 12:55:33 in r'-filter.  We detect the optical afterglow 
(Troja et al., GCN  29233; Xin et al., GCN 29235; Hu et al., GCN 29236; 
Hosokawa et al., GCN  29237).

Preliminary photometry of the afterglow obtained in a few initial 
imaging is following

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

2021-04-01 12:55:33  0.0632  r'(AB)  5*60   17.97 0.06   22.7

The photometry is based on nearby stars of PanSTARRS-PS1.
Observations is continuing.