TITLE:   GCN CIRCULAR
NUMBER:  15144
SUBJECT: GRB 130831A: Gemini-North Redshift
DATE:    13/08/31 15:37:32 GMT
FROM:    Antonino Cucchiara at UCSC/UCO Lick  <acucchia@ucolick.org>

A. Cucchiara (UCSC/UCO Lick Observatory), D. Perley (Caltech) 
report on behalf of a larger collaboration:

"We observed the afterglow of GRB 130831A (Hagen et al. 
GCN 15139, Guidorzi et al. GCN 15140) with the GMOS spectrograph 
on Gemini-North, beginning approximately 50 min after the BAT trigger.

We obtained 2x900s exposure spectra under exquisite conditions 
using the B600 grism, covering the 3860-6649 Angstrom wavelength range.

In our preliminary analysis we detect MgII2796,2803 doublet and 
MgI2853 absorption lines at z=0.4791.

No other strong features are detected in absorption or in emission, 
therefore we suggest this as the redshift of GRB 130831A.


We thank the Gemini-N staff, in particular Adam Smith and 
Anthony Matulonis, for their support."