[vsnet-grb-info 9429] GRB 100628A: Gemini North Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  10909
SUBJECT: GRB 100628A: Gemini North Observations
DATE:    10/06/29 17:46:37 GMT
FROM:    Andrew Levan at U.of Leicester  <A.J.Levan at warwick.ac.uk>

A.J. Levan (U. Warwick), N.R. Tanvir, K. Wiersema (U. Leicester),
S.B. Cenko (UC Berkeley) report on behalf of a larger collaboration:

"We obtained two epochs of observations of GRB 100628A (Immler et
al. GCN 10895) with Gemini-North. The first was obtained starting
at 28 Jun, 08:59 UT, approximately 43 minutes after the burst, with
a second obtained on 29 Jun 05:50 UT, ~21.5 hours after the burst.
A total of 1200s of exposure time were obtained in the i-band. Our
images covers ~90% of the BAT refined error circle (Barthelmy et
al GCN 10896), including the position of the candidate X-ray afterglow
identified by Starling et al. (GCN 10899; 10907).

Digital image subtraction performed between the two epochs does not
reveal any candidate variable sources between the two epochs, to
an approximate limiting magnitude of i~24. In particular, we do not
find any evidence for variability in any of the galaxies identified
by Berger et al. (GCN 10902) surrounding the XRT location,
including G1, which now lies within the XRT error circle
(Starling et al. GCN 10907; Berger et al. GCN 10908)

We also note the presence of two, apparently point like sources
lying within the refined XRT error circle, at locations of

S1:
RA(J2000) 15:03:53.45
DEC(J2000) -31:39:54.2

S2:
RA(J2000)  15:03:53.73
DEC(J2000) -31:39:48.4

Both are unresolved at the resolution of our observations, but
neither show apparent variability between the two epochs.

An image, showing the field as observed by Gemini-North can be found
at

http://www.star.le.ac.uk/~anl/100628A

We thank the staff of Gemini-North for their assistance with these
observations."