TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4384
SUBJECT: GRB 051221: Redshift from Gemini
DATE:    05/12/22 09:33:06 GMT
FROM:    Edo Berger at Carnegie Obs  <eberger@ociw.edu>

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

"We obtained 2x1200 sec spectra of the afterglow + host galaxy of the
short GRB 051221 (GCN 4383) with Gemini/GMOS.  We detect several strong
emission lines at the position of the afterglow+host which we identify as
[OIII]4959,5006, H-beta, and [OII]3727 at a redshift of z=0.5465.  Weak
absorption at the CaII H&K and G-band wavelengths at the same redshift may
also be present, but at a low significance.

The detection of strong emission lines indicates that the host galaxy is
under-going active star formation, and is possibly similar to that of GRB
050709 (Fox et al. 2005).

At the redshift of 0.5465, the isotropic-equivalent gamma-ray energy 
release of the burst is 9e50 erg, the highest measured to date."