GCN Circular 19936
A. Volnova (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), E. Mazaeva (IKI), I. Korobtsev (ISTP) report on behalf of larger GRB follow-up collaboration: We observed the field of the GRB 160917A (Racusin et al. GCN 19926) with AZT-33IK telescope of Sayan observatory (Mondy) starting on Sep., 18 (UT) 15:25:21. We obtained several images in R-filter. We do not detect the optical source reported as afterglow candidate (Volnova et al. GCN 19929; Kuin et al. GCN 19931). Preliminary photometry of the field is following Date UT start t-T0 Filter Exp. OT UL (3 sigma) (mid, days) (s) 2016-09-18 15:25:21 1.18522 R 60*60 n/d 22.0 Photometry is based on nearby USNO-B1.0 stars used in GCN circ. 19929. In comparison with our previous observation (Volnova et al. GCN 19929) the source is not visible up to 22.0 mag. The source faded between two epochs on at least 1.4 magnitudes and it is most probably the afterglow of GRB 160917A. Our observation is compatible with more deep RATIR observation in r-filter (Butler et al. GCN 19933).