[vsnet-grb-info 27409] GRB 210212B (TF21aakruew/AT2021cwd): Assy optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29512
SUBJECT: GRB 210212B (TF21aakruew/AT2021cwd): Assy optical observations
DATE:    21/02/16 13:44:36 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

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

We observed the optical transient of ZTF21aakruew/AT2021cwd (Yao et al., 
GCN 29508) which is probably an afterglow of GRB 210212B (Svinkin et 
al., GCN 29511) with AZT-20 telescope of Assy-Turgen observatory 
starting on 2021-02-15 (UT) 17:33:23. The optical transient is 
marginally detected in a stacked image in r'-filter.

Preliminary photometry of the object  is following
Date       UT start   t-T0    Filter  Exp.   OT    S/N  Err.  UL(3sigma)
                             (mid, days)     (s)

2021-02-15 17:33:23   3.64231  r'     59*60  23.8  2.5  0.5   23.6

The photometry is based on nearby SDSS-DR12 stars
RA DEC r dr
10:24:36.66048 +11:35:29.6088 18.206 0.008
10:24:34.08528 +11:36:05.0220 17.486 0.006
10:24:47.98080 +11:38:11.0832 15.153 0.003

The midtime value (t-T0) given in the table above  was counted from GRB 
trigger of 2021-02-12 (UT) 02:37:57 (Svinkin et al., GCN 29511).

The power-law index  of the light curve (alpha ~ 1.7) is consistent with 
an afterglow after jet break. The light curve can be found in

http://grb.rssi.ru/GRB210212B/GRB210212B_LC.png