TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4419
SUBJECT: GRB 051227: Likely host galaxy underlying afterglow position
DATE:    05/12/30 20:12:59 GMT
FROM:    Edo Berger at Carnegie Obs  <eberger@ociw.edu>

E. Berger (Carnegie Observatories) and A. M. Soderberg (Caltech) report:

"We re-observed the error circle of GRB 051227 with Gemini/GMOS starting
on 2005 Dec. 30.35 UT (62.6 hr after the burst) for a total of 30 min in
r-band.  Source S1 is clearly detected in our summed image with
r=25.8+/-0.2 mag.

Digital subtraction performed on this image and the previous two Gemini
images obtained on nights 1 and 2 (13.9 and 38.6 hr after the burst,
respectively; GCN 4414) reveals that following a decline of about 1 mag
between nights 1 and 2 (CGNs 4412,4413,4414), there has been no change in
flux between nights 2 and 3.  This suggests that unless there has been a
significant flatenning in the afterglow decay, our detection of source S1
on night 3 represents the host galaxy of GRB 051227 and that the galaxy at
z=0.714 located 4.7" to the NE (GCNs 4408,4409) is unrelated to the burst.  
Thus, the offset of GRB 051227 relative to its host is negligible, and the
actual redshift of the burst is most likely higher than z=0.7.

Therefore, GRB 051227 is either one of the highest redshift short GRBs
detected to date, or given the similarity in brightness to the hosts of
long GRBs, and the ambiguity as to the nature of the burst (GCN 4401), it
is in fact a long GRB."