TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4291
SUBJECT: GRB 051117B: R and I observations of possible host galaxy
DATE:    05/11/18 13:19:34 GMT
FROM:    Christina Thoene at Niels Bohr Institute,DARK Cosmo Ctr  <cthoene@astro.ku.dk>

C. Thoene and C. Feron, P. Jakobsson, B.L. Jensen, J.P.U. Fynbo,
J. Sollerman, H. Pedersen, D. Watson, J. Hjorth (DARK Cosmology Centre,
NBI) report:

We observed the field of GRB 051117B (Band et al. GCN 4281) with DFOSC at
the Danish 1.54m telescope on La Silla from 18 Nov 2005 starting at 02:58
UT. Exposures of 8 x 600s in R and 18 x 600s in Gunn-i were obtained with
a seeing of 1.5".

We detect an extended source lying on the edge of the XRT error circle
(Beardmore et al. GCN 4282) in both bands as found by Chen et al. in R
(GCN 4285). The source is centered at: (RA,Dec)(J2000.0) =
(05:40:43.26,-19:16:26.1). No other sources are detected in or near the
XRT-circle, nor were there any appreciable brightness variations in the
extended source during our observations.

Using preliminary photometric zeropoints we estimate the following
magnitudes for this source:  21.0 in R and 20.4 in Gunn-i and a color
index of R-I=0.6.

We estimate the probability to find a similar galaxy by chance in the
error-circle to be 5% (based on Postman et al. ApJ 506, 33 (1998)). If the
extended source is the host galaxy associated with GRB 051117B, this would
be one of the brightest host galaxies of long-duration Swift GRBs.

A finding chart of the field is available at:
http://www.astro.ku.dk/~brian_j/grb/grb051117.558/