TITLE: GCN CIRCULAR NUMBER: 15188 SUBJECT: GRB 130831A: ISON-Kislovodsk optical observations DATE: 13/09/07 23:52:12 GMT FROM: Alexei Pozanenko at IKI, Moscow A. Volnova (IKI), V. Linkov (ISON), K. Polyakov (ISON), D. Ivanov (ISON), I. Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the afterglow (Hagen et al., GCN 15139; Guidorzi et al., GCN 15140) of the Swift GRB 130831A (Hagen et al., GCN 15139) with SANTEL-400AN telescope of ISON-Kislovodsk observatory starting on Aug. 31 (UT) 19:12:30. We took several unfiltered images. Preliminary photometry of combined images is following T_start T0+ Filter, Exposure, OT, OT_err (UT) (mid, d) (s) 2013-08-31T19:12:30 0.26113 none 840 18.32 0.08 2013-08-31T19:28:20 0.27212 none 840 18.44 0.10 2013-08-31T19:47:24 0.29470 none 1760 18.47 0.13 The photometry is based on reference stars SDSS-DR9, (R mag, transformation by Lupton 2005) N SDSS id R(Lupton)errR 1 J235443.71+292539.3 13.491 0.016 2 J235438.60+292547.3 14.136 0.015 3 J235423.64+292452.8 17.120 0.016