TITLE: GCN CIRCULAR NUMBER: 16809 SUBJECT: GRB 140907A: TShAO observations DATE: 14/09/09 20:54:38 GMT FROM: Alexei Pozanenko at IKI, Moscow A. Volnova (IKI), A. Pozanenko (IKI), W. Mundrzyjewski (Fesenkov Astrophysical Institute), V. Tereshenko (Fesenkov Astrophysical Institute) report on behalf of larger GRB follow-up collaboration: We observed the field of the Swift GRB 140907A (Krimm et al., GCN 16788)with Zeiss-1000 (East) telescope of Tien Shan Astronomical Observatory starting on Sep. 07, (UT) 17:05. We took several images in R-filter. Within enhanced XRT error circle (Goadet al., GCN 16795) we clearly detect the afterglow(Xu et al., GCN 16789; Kuin and Krimm, GCN 16791). Preliminary photometry of first and last exposures is following Date UT start t-T0,d Exp,s Filter OT OT_err (mid) 2014-09-07 17:33:41 0.06357 600 R 18.94 0.08 2014-09-07 23:22:46 0.30598 600 R 20.22 0.07 The photometry is based on nearby USNO-B1.0 stars, R2 magnitudes. Preliminary light curve of the afterglow of GRB 140907A obtained between (UT) 17:33:41 and 23:22:46 can be found in http://grb.rssi.ru/GRB140907A/GRB14907A_lc.png . Within the time interval ( 17:33:41 - 23:22:46 ) the LC might be approximated by power law with a power law index ~-2 which could suggest the jet-brake within this interval.