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GCN Circular 21300

GRB 170705A: ISON/Terskol optical observations
2017-07-06T13:28:01Z (7 years ago)
Alexei Pozanenko at IKI, Moscow <>
E. Mazaeva (IKI), A. Pozanenko (IKI), V. Agletdinov (KIAM), A. Volnova 
(IKI),  A. Mokhnatkin (KIAM),   I. Molotov (KIAM)  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; Svinkini et al., GCN 21299) with K-800 (0.8m) telescope  of 
ISON/Terskol  observatory starting  on July, 05 (UT) 18:30:54.  We obtained 
several unfiltered images of 20 s exposure. 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 
clearly visible in a combined image. Preliminary  photometry of the 
afterglow is following

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

2017-07-05  18:30:54 0.70649 CR      358*20 19.84 0.08 22.2

Photometry is based on nearby SDSS DR9 stars
SDSS id                          R_Lupton
J124702.82+181926.7 17.63
J124700.96+181851.9 19.15
J124653.35+182058.9 17.08
J124641.28+182043.7 16.61
J124646.57+181522.1 17.45
J124645.71+181510.4 17.18
J124650.58+182306.3 18.18
J124624.60+181820.0 16.34
J124647.75+181330.6 16.05
J124644.99+181414.3 18.79
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