[vsnet-grb-info 16894] GRB 150818A: Mondy optical observations
GCN Circulars
gcncirc at capella2.gsfc.nasa.gov
Thu Aug 20 01:25:19 JST 2015
TITLE: GCN CIRCULAR
NUMBER: 18175
SUBJECT: GRB 150818A: Mondy optical observations
DATE: 15/08/19 16:25:12 GMT
FROM: Alexei Pozanenko at IKI, Moscow <apozanen at iki.rssi.ru>
E. Mazaeva (IKI), E. Klunko (ISTP), A. Volnova (IKI), I. Korobtsev
(ISTP), A. Pozanenko (IKI) report on behalf of larger GRB follow-up
collaboration:
We observed the field of Swift GRB 150818A (D'Elia et al., GCNC 18152)
with AZT-33IK telescope of Sayan observatory (Mondy) starting on Aug.,
18 (UT) 15:07:42. We obtained several images in R-filter of 120 s
exposure. The source previously mentioned (McCauley et al., GCN 18161;
Schulze et al., GCN 18164) is clearly visible. Coordinates of the
source are (J2000) 15:21:25.56 +68:20:32.0 with uncertainty of 0.3
arcsec in both coordinates. Preliminary photometry of the source is
following
Date UT start t-T0 Filter Exp. OT Err.
(mid, days) (s)
2015-08-18 15:07:42 0.16843 R 31*120 20.25 0.08
Photometry is based on USNO-B1.0 stars:
USNO-B.1_id R2
1583-0162302 16.65
1583-0162268 17.48
1583-0162214 16.71
1583-0162248 19.43
We can suggest the source as shallow fading afterglow because the source
is significantly faded between our observations (R=20.25+/-0.08 at 4 hrs
after burst trigger) and NOT observations at 9.62 hrs (Schulze et al.,
GCN 18164).
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