[vsnet-grb-info 12052] GRB 120711A Gemini-S likely redshift

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13441
SUBJECT: GRB 120711A Gemini-S likely redshift 
DATE:    12/07/11 12:46:35 GMT
FROM:    Nial Tanvir at U.Leicester  <nrt3 at star.le.ac.uk>

N. R. Tanvir, K. Wiersema (U. Leicester), A. J. Levan (U. Warwick),
D. Fox (Penn State), A. Fruchter (STScI) and D. Krogsrud (Gemini)
report on behalf of a larger collaboration:

We observed the afterglow of GRB 120711A (Gotz et al. GCN 12434;
Lacluyze et al. GCN 12430) using the GMOS-S spectrograph on Gemini-South.

Observations began at 2012-7-11 10:08 UT, about 7.5 hr post-burst.
The data were obtained at high air-mass and on the boundary of twilight,
so the signal-to-noise is rather poor.  Nevertheless,
in the spectrum we identify lines of MgII (2797/2804A) and
FeII (2374/2383/2587/2600A) at a common redshift of z=1.405.

This therefore provides a robust lower-limit to the redshift of the GRB.
Furthermore, given the lack of other absorption features, in particular
any matching a redshift z~3 (Elliott et al. GCN 13438), we tentatively
identify z=1.405 as the most likely GRB redshift.