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GCN Circular 18097

Subject
GRB 150728A: TSHAO optical observations
Date
2015-07-30T18:41:10Z (9 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
E. Mazaeva (IKI), I. Reva (Fesenkov Astrophysical Institute),   A. 
Volnova (IKI), A. Pozanenko  (IKI) report on behalf of larger GRB 
follow-up collaboration:

We observed the field of the Swift GRB 150728A (Krimm et al. GCN 18087) 
   with Zeiss-1000 (East) 1-m telescope of Tien Shan Astronomical 
Observatory starting on Jul. 29 (UT) 18:34:50.  We obtained several 
images in R-filter.  In a combined image we do not detect the FTN object 
(Dichiara et al. GCN 18090) also visible in AAO observations (Mazaeva et 
al., GCN 18094) and source A in RATIR observations (Watson  et al., GCN 
18096).
A photometry of the field is following

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

2015-07-29 18:34:50    1.26425  R       15*300   21.2

The photometry is based on nearby USNO-B1.0 stars
USNO-B.1_id  R2
1239-0338943 17.06
1239-0338998 16.69

Also we marginally detect object B of the  RATIR observations (Watson 
et al., GCN 18096) in our current and previous observation of the field 
(Mazaeva et al., GCN 18094).

The finding chart can be found in 
http://grb.rssi.ru/GRB150728A/GRB150728A_AAO_left_TSHAO_right.png

Would the source A be a  non-variable point like object with magnitudes 
of  r=21.37+/-0.04 and   i=20.89+/-0.04 (Watson  et al., GCN 18096) in 
our observation the object A might be detected  as the object with a 
magnitude less than R=21.3 (3 sigma). So we tentatively suggest the 
object A as an afterglow candidate.
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