TITLE:   GCN CIRCULAR
NUMBER:  14455
SUBJECT: GRB 130427A: Gemini-North redshift
DATE:    13/04/27 11:43:31 GMT
FROM:    Andrew Levan at U.of Leicester  <A.J.Levan@warwick.ac.uk>

A.J. Levan (U. Warwick), S.B. Cenko (U.C. Berkeley), D.A. Perley
(Caltech) and N.R. Tanvir (U. Leicester) report for a larger
collaboration:

We obtained spectroscopy of the afterglow of GRB 130427A (Maselli
et al. GCN 14448, Elenin et al. GCN 14450, Perley et al. GCN 14451)
with Gemini-North / GMOS, begininnig at 09:19 UT roughly 1.5 hours
after the burst. Two different central wavelengths were observed
giving a coverage from ~3100-6700 A. The resulting spectra are of
very high signal to noise given the brightness of the afterglow.
In these spectra we identify absorption lines due to Ca H and K,
Mg I as well as the Mg II doublet at a common redshift of z=0.34.
We suggest this to be the redshift of GRB 130427A.

We do not see evidence for emission lines from an underlying host,
although given the brightness of the afterglow this is not surprising.
The absolute magnitude of object in SDSS, if at z=0.34 is M_R ~
-19.7, relatively bright for a GRB host.

We thank the Gemini-staff for their help in rapidly obtaining these
observations.