TITLE:   GCN CIRCULAR
NUMBER:  15961
SUBJECT: GRB 140311A: Gemini-South redshift
DATE:    14/03/12 11:51:40 GMT
FROM:    Nial Tanvir at U.Leicester  <nrt3@star.le.ac.uk>

N. R. Tanvir (U. Leicester), A. J. Levan (U. Warwick),
K. Wiersema (U. Leicester), A. Cucchiara (NASA/GSFC) report:

We observed the afterglow of GRB 140311A (Racusin et al. GCN 15944;
Xu et al. GCN 15947) with Gemini-South using the GMOS-S spectrograph,
beginning March 12 08:24 UT, approximately 11.3 hours post-trigger.
The spectrograph was configured to cover wavelength range from
about 4000 AA to 6700 AA.

The optical trace of the afterglow is clearly detected, with many
absorption lines suggesting we are only seeing the region
blueward of Ly-alpha in the rest frame.  Based on several strong 
absorption features and a break, which would correspond to Ly-beta, 
Ly-gamma, Ly-delta and the Ly-limit at approximately z=4.95, we 
conclude this is likely to be the redshift of the GRB. Further
analysis of the spectrum is ongoing.

We thank the observatory staff, particularly Peter Pessev,
for excellent support in obtaining these observations.