TITLE:   GCN CIRCULAR
NUMBER:  6450
SUBJECT: GRB070521: Gemini Observations
DATE:    07/05/22 03:13:53 GMT
FROM:    S. Bradley Cenko at Caltech  <cenko@srl.caltech.edu>

S. B. Cenko (Caltech), P. A. Price (IfA/Hawaii), and E. Berger (OCIW)
report on behalf of a larger collaboration:

We have imaged the field of GRB070521 (Guidorzi et al.; GCN 6431) with the
Gemini Multi-Object Spectrograph (GMOS) and the Near-Infrared Imager
(NIRI) mounted on the Gemini North Telescope.  Observations were taken in
the g', i', z' (GMOS) and J, H, Ks (NIRI) filters, beginning at 7:36:54
UT on 21 May 2007.

We weakly detect the host candidate proposed by Hattori, Aoki, and Kawai
(GCN 6444) only in our i'- and Ks-band images.  In the table below we
report a summary of our observations.  Photometric calibration was
performed relative to SDSS (Cool et al.; GCN 6432) for the GMOS images
and the 2MASS point source catalog for our NIRI imaging.

Filter		t - t_b (hr)	Exposure (s)	Magnitude
-------------------------------------------------------------------------
g'		1.08		2 x 180		> 25.0
i'		1.21		2 x 180		~ 24.1
z'		1.33		4 x 180		> 23.0
J		1.92		15 x 30		> 21.5
H		2.20		15 x 30		> 21.0
Ks		2.50		15 x 30		~ 22.3