[vsnet-grb-info 19577] GRB 170705A: TShAO optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21320
SUBJECT: GRB 170705A: TShAO optical observations
DATE:    17/07/11 17:39:03 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

A. Volnova (IKI),  E. Mazaeva (IKI), A. Pozanenko (IKI), A. Kusakin 
(Fesenkov Astrophysical Institute),  I. Reva (Fesenkov Astrophysical 
Institute)    report on behalf of larger GRB follow-up collaboration:

We observed the field of the Swift GRB 170705A (Starling et al. GCN 
21289) which is also detected by GBM/Fermi and Konus-Wind  (Bissaldi  et 
al., GCN 21297; Svinkin et al., GCN 21299)  with Zeiss-1000 1-m 
telescope of Tien Shan Astronomical Observatory on July 6-8.  We took 
several images in R-filter.  The optical afterglow  of GRB 170705A 
(Starling et al. GCN 21289, Lipunov et al. GCN 21291, Butler et al. GCN 
21293, Emery et al. GCN 21294; Ugarte Postigo et al. GCN 21298)  is 
visible in a combined image on July 6, and upper limit only for July 
7-8. Preliminary  photometry of the afterglow is following.

Date       UT start   t-T0    Filter Exp.  OT     Err. UL
                      (mid, days)     (s)             (3 sigma)

2017-07-06 16:28:29  1.61411  R    38*180  20.67  0.24 21.1
2017-07-07 17:30:55  2.63106  R    13*180  n/d    n/d  20.6
2017-07-07 17:30:55  3.10501  R    34*180  n/d    n/d  21.1

Photometry is based on nearby SDSS DR9 stars listed in GCN 21300.