TITLE:   GCN CIRCULAR
NUMBER:  20516
SUBJECT: GRB 170121B:  AbAO optical observations
DATE:    17/01/24 17:41:03 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

E. Mazaeva (IKI), A. Pozanenko (IKI), R. Inasaridze (AbAO), A. Volnova 
(IKI),  V. Ayvazian  (AbAO),  O.Kvaratskhelia (AbAO), G. Inasaridze (AbAO), 
I. Molotov (KIAM), report on behalf of larger GRB follow-up collaboration:

We observed the field of optical transient reported by Lipunov et al. (GCN 
20502) as a possible candidate of the Fermi/GBM GRB 170121B (Hamburg et al. 
GCN Circ. 20505) and XRT  afterglow  candidate reported by Sbarufatti  et 
al. (GCN  20510) with AS-32 (0.7m) telescope of Abastumani Observatory 
starting on Jan., 23 (UT)  16:14:49. We obtained several unfiltered images 
of the field.  We do not find any source at coordinates of the optical 
transient (Lipunov et al., GCN  20502). Within XRT error circle  (Sbarufatti 
et al., GCN  20510) we find the source which is also presented in DSS2 and 
USNO-B1.0 as the star USNO-B1.0 0807-0048671 (magnitudes R1 = 17.94, R2 = 
17.07). Preliminary photometry  of the source and the field of  the optical 
transient (Lipunov et al., GCN  20502) is following

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

2017-01-23 16:14:49.   2.09866   CR     60*60  17.76  0.07  22.9

Photometry is based on nearby USNO-B1.0 stars (R2 magnitudes)
USNO-B.1_id    R2
0807-0048576 16.37
0806-0049543 18.47
0807-0048525 17.28
0807-0048536 17.23
0806-0049637 15.57
0807-0048826 15.71
0807-0048833 15.41
0807-0048816 17.22