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 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