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GCN Circular 18097

GRB 150728A: TSHAO optical observations
2015-07-30T18:41:10Z (9 years ago)
Alexei Pozanenko at IKI, Moscow <>
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 
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

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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