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GCN Circular 21333

GRB 170711A: ISON/Terskol and AbAO optical observations
2017-07-13T18:13:15Z (7 years ago)
Alexei Pozanenko at IKI, Moscow <>
A. Volnova (IKI),   A. Pozanenko (IKI),  A. Mokhnatkin (KIAM),  R. 
Inasaridze (AbAO), E. Mazaeva (IKI), V. Agletdinov (KIAM),   V. Ayvazian 
(AbAO),  O. Kvaratskhelia (AbAO), G. Inasaridze (AbAO),    I. Molotov (KIAM) 
report on behalf of  larger GRB follow-up collaboration:

We observed the field of the Swift GRB 170711A (D'Elia  et al. GCN 21321) 
with K-800 (0.8m) telescope  of  ISON/Terskol observatory starting on July, 
12 (UT) 00:00:39 and  AS-32 telescope of AbAO starting  on July, 11 (UT) 
23:58:46, i.e. about 1.6 hours after GRB trigger.  We obtained
several unfiltered images. We do not detect any source in stacked images 
within the enhanced XRT position (Beardmore  et al. GCN 21323).
Preliminary  photometry of the field is following

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

2017-07-11   23:58:46 0.07894 CR      11*60 n/d n/d  17.0     AS-32
2017-07-12   00:00:39 0.07658 CR      45*25 n/d n/d  19.1     K-800

Photometry is based on nearby stars of USNO-B1.0
USNO-B1.0_id   R2
1378-0084355   14.59

1378-0084262   15.13

1378-0084218   14.70

We detect the object in  coordinates (J2000)  03 03 11.46  +47 50 56.1  (+/- 
0.5 arcsec) which is 7.7 arcsec apart from a center of the enhanced XRT 
position. The object is clearly detected in the stacked image of K-800  and 
marginally seen at  the same position with AS-32 stacked image. The 
brightness of the object is 18.56 +/- 0.25 based on the reference stars 
listed above. The object is absent in the  USNO-B1.0. At present, it is not 
clear whether this object has any relation to the GRB 170711A.
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