TITLE:   GCN CIRCULAR
NUMBER:  23661
SUBJECT: GRB 190106A: optical observations, possible jet break detection
DATE:    19/01/09 18:42:15 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI),  A. Pozanenko (IKI), P. Minaev (IKI), E. Klunko (ISTP), 
I. Reva (FAPI), M. Krugov (FAPI), V. Rumyantsev (CrAO), R. Ya. 
Inasaridze (AbAO), E. Mazaeva (IKI), A. Volnova (IKI)   report   on 
behalf of IKI-FuN:

We continue observations the optical afterglow (e.g. Lipunov  et al. 
GCN 23616, Itoh et al. GCN 23617, Mao et al. GCN 23618, Reva et al., GCN 
23620, Xin et al. GCN 23622, Quadri et al. GCN 23624, Hu et al. GCN 
23627)  of  the GRB 190106A (Sonbas et al., GCN 23615)  with AZT-33IK 
telescope of Sayan observatory (Mondy), Zeiss-1000 1-m telescope of Tien 
Shan Astronomical Observatory, and  AS-32 (0.7m) telescope of Abastumani 
Observatory.  Preliminary photometry of the afterglow is following.

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

2019-01-07 17:27:12 1.19251 R      63*60  20.27 0.08  AbAO
2019-01-08 11:07:16 1.91774 R      30*120 21.11 0.13  Mondy
2019-01-08 15:53:23 2.09628 R      12*120 21.1  0.3   CrAO


The photometry is based on nearby SDSS  stars
SDSS-DR12_id              R(Lupton)
J015920.22+235150.7 16.475
J015929.35+235237.5 15.774

Based on our previous results (GCNs 23620, 23638, 23640) and photometry 
above we plot a light curve  ( 
http://grb.rssi.ru/GRB190106A/GRB190106A_LC_R_fit.png ). We could 
suggest the jet break at 1.5 +/- 0.5 days.