TITLE:   GCN CIRCULAR
NUMBER:  20893
SUBJECT: GRB 170317A: Mondy optical observations
DATE:    17/03/17 16:48:01 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

E. Mazaeva (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), A. Volnova
(IKI)  report on behalf of larger GRB follow-up collaboration:

We observed the field of  GRB 170317A (LaPorte et al., GCN  20885) with 
AZT-33IK telescope of Sayan observatory (Mondy) starting on  March, 17 
(UT) 13:56:13. We obtained 60 of 60 s exposure images in R-filter.
The optical afterglow (LaPorte et al., GCN 20885; Mazaeva et al., GCN 
20886; Xin et al., GCN 20888; Mao  et al., GCN 20889) is clearly visible 
in stacked images. Preliminary photometry of the afterglow is following

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

2017-03-17 13:56:13  0.18073  R      20*60    20.94  0.10  22.5

The photometry is based on nearby USNO-B.10 stars
Ref.stars
USNO_B1_id   R2
1405-0167493 16.10
1405-0167631 15.69
1404-0169027 16.03
1405-0167512 16.85
1404-0169128 16.25