TITLE:   GCN CIRCULAR
NUMBER:  17081
SUBJECT: GRB 141121A: Keck redshift
DATE:    14/11/21 12:23:41 GMT
FROM:    Daniel Perley at Caltech  <dperley@astro.caltech.edu>

D. A. Perley, C. P. Ott (Caltech), M. Modjaz, and D. Fierroz (NYU) report:

We acquired a spectrum of the afterglow of GRB 141121 (Lien et al., GCN 
17075; Tanga et al., GCN 17078) using the Low-Resolution Imaging 
Spectrometer (LRIS) on the Keck I 10-meter telescope.  A single exposure 
of 900 seconds was acquired using the B600 and R400 gratings, covering a 
wavelength range from 3116 to 10264 Angstroms.

In the reduced spectrum, we identify the Mg II (2796,2803) doublet, the 
Fe II (2599) doublet, Fe II (2585), and Fe II (2344) at a common 
redshift of z=1.47 (as well as many absorption lines at bluer 
wavelengths).  No higher-redshift absorption systems are observed and no 
DLA is present down to the blue limit of our spectrum (suggesting an 
upper limit of z<1.56) so we associate this with the redshift of the GRB.