[vsnet-grb-info 15520] GRB 140907A: TShAO observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16809
SUBJECT: GRB 140907A: TShAO observations
DATE:    14/09/09 20:54:38 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

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.