GCN Circular 18097
Subject
GRB 150728A: TSHAO optical observations
Event
Date
2015-07-30T18:41:10Z (11 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.