TITLE: GCN CIRCULAR NUMBER: 15190 SUBJECT: GRB 130831A: Maidanak optical observations DATE: 13/09/08 00:17:41 GMT FROM: Alexei Pozanenko at IKI, Moscow A. Pozanenko (IKI), A. Volnova (IKI), B. Hafizov (UBAI), O. Burhonov (UBAI) 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 AZT-22 telescope equipped with SNUCAM of Maidanak observatory in R filter. A preliminary photometry of combined images is based on SDSS stars (see at the bottom): T_start T0+ Filter, Exposure, OT (UT) (mid, d) (s) 2013-09-02T13:58:23 2.0410 R 1x600 22.20 +/- 0.10 2013-09-04T18:47:13 4.2555 R 5x600 22.53 +/- 0.07 2013-09-05T18:57:03 5.2658 R 6x600 22.90 +/- 0.07 A preliminary lc of the afterglow GRB 130831A based on our GCNs ##15185, 15186, 15188, 15189 and reported in this circular can be found in http://grb.rssi.ru/GRB130831A/grb130831A_lc_preliminary.PNG A power-law decay of the lc between 0.1 days and 2 days after trigger is -1.68 +/- 0.06 and marginally consistent with power-law decay reported by Watson (GCN 15179). Reference stars 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