TITLE:   GCN CIRCULAR
NUMBER:  27574
SUBJECT: GRB 200412B: contunued AbAO optical observations
DATE:    20/04/14 10:19:21 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI), A. Pozanenko (IKI), R. Ya. Inasaridze (AbAO), V.R. 
Ayvazian (AbAO),  G. V.  Kapanadze (AbAO),   E. Mazaeva (IKI), A. 
Volnova  (IKI),  I. Molotov (KIAM) report on behalf of  GRB IKI FuN:

We observed the field of GRB 200412B (Fermi GBM team, GCN 27547; Mailyan
et al., GCN 27558; see also Burgess et al., GCN 27548; Longo et al., GCN
27557; Page et al., GCN 27561; Gupta et al., GCN 27563; Zheng et al., 
GCN 27565)  with AS-32 (0.7m) telescope of Abastumani Observatory 
starting on 2020-04-14 (UT) 00:16:57.  We  clearly detected  the 
afterglow of GRB 200412B  (Lipunov et al., GCNs 27555, 27556; Kumar et 
al., GCN 27564; Belkin et al., GCN 27566, Stecklum et al., GCN 27567,
Moskvitin GCN 27570; Xin  et al., GCN 27571).  Preliminary photometry of 
the afterglow is following.

Date       UT start  t-T0    Filter Exp.  OT    Err. UL
                     (mid, days)     (s)
2020-04-14 00:16:57  1.65401 R      67*60 20.7 0.1   22.1

The photometry is based on nearby USNO-B1.0 stars
UUSNO-B1.0_id R2
1525-0302108 17.21
1524-0300914 17.20
1525-0301929 17.85

The index of power law decay of the afterglow light curve between the 
two epochs of our observations (Belkin et al., GCN 27566 at 0.41793 
days) and reported in this circular (at 1.65401 days) is -1.58+/-0.07 
which is corroborate with the index reported by Xin  et al. (GCN 27571).