TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3401
SUBJECT: GRB 050509b: Further Analysis of Keck LRIS Images
DATE:    05/05/10 03:13:47 GMT
FROM:    S. Bradley Cenko at Caltech  <cenko@srl.caltech.edu>

S. Bradley Cenko, B. T. Soifer, Chao Bian, Vandana Desai, S. R. Kulkarni
(Caltech), Edo Berger (Carnegie), Arjun Dey and Buell T. Jannuzi (NOAO)
report on behalf of a larger collaboration:

Further to our GCN 3391 we obtained an additional LRIS image in g and R
band. The sum of these three epochs centered on the fading X-ray source
(GCN 3395) is shown at

http://www.srl.caltech.edu/~cenko/grb050509b/050509b_zoom.jpg

In addition to the elliptical galaxy discussed in GCN 3386, there
are four sources listed below.

------------------------------------------------------------------------
Source		RA (J2000.0)	Dec (J2000.0) 	Dist from X-ray source
------------------------------------------------------------------------
S1              12:36:13.7      28:58:57.3      4.5"
S2		12:36:14.1	28:58:59.6	3.0"
S3		12:36:14.0	28:59:01.5	1.4"
S4		12:36:13.7	28:59:02.5     	3.0"

Source S1 was proposed as a candidate by its proximity to the
elliptical galaxy (GCN 3388) and by its possible variability (GCN 3391).
However, as noted earlier and now confirmed with more data, source S1
is clearly extended. The color and a low resolution (LRIS) spectrum of
S1 show it to be a blue object.  A simple interpretation of the data is
that source S1 a high redshift star-forming galaxy.

The optical counterpart of the fading X-ray source has not yet been
securely identified. To this end we are undertaking detailed analysis of
the LRIS images."