TITLE:   GCN CIRCULAR
NUMBER:  17366
SUBJECT: GRB 150120B: Khureltogot optical observations
DATE:    15/01/30 21:25:11 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

E. Mazaeva (IKI), S. Schmalz (AIP), N. Tungalag (Research Center of 
Astronomy and Geophysics MAS),  A. Volnova (IKI), I.Molotov (KIAM), A. 
Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:

We observed the field of GRB 150120B  (D'Elia et al., GCN 17314) with 
ORI-40 telescope of Khureltogot observatory on Jan., 20  starting on 
(UT) 10:52:51. We obtained 90 unfiltered images of 60 s exposure. 
Within  enhanced Swift-XRT error circle (Goad et al., GCN 17320)  we 
clearly detect optical  afterglow (Perley et al. GCN 17315, Guidorzi et 
al. GCN 17316) in a combined image. Photometry of the afterglow is 
following

Date        UT start  t-T0       Filter  Exp.   OT    OT_err
                       (mid, days)        (s)

2015-01-20  10:52:51  0.18068    none    90*60  20.75 0.20

The photometry is based on R magnitudes of nearby USNO-B1.0 stars

USNO-B1_id   R2
0981-0032639 16.04
0981-0032644 17.10