TITLE:   GCN CIRCULAR
NUMBER:  16797
SUBJECT: GRB 140907A: redshift from the 10.4m GTC telescope
DATE:    14/09/08 08:01:07 GMT
FROM:    Alberto Castro-Tirado at Inst.de Astro. de Andalucia  <ajct@iaa.es>

A.J. Castro-Tirado (IAA-CSIC/ISA-UMA), J. Gorosabel (IAA-CSIC/UPV-EHU) and
A. Garcia-Rodriguez (GTC-IAC), report on behalf of a larger collaboration:

We observed the optical afterglow of GRB 140907A (Krimm et al. GCN 16788;
Kuin et al. GCN 16791; Masi et al. GCN 16792, Kuroda et al. GCN 16793)
with the 10.4m GTC (+OSIRIS). Spectroscopic observations started at
05:29:33 UT (13.4 hours post GRB). Two 500s spectra were obtained with the
R1000B and R1000R grisms, covering the range between 3800 and 9900 A, at a
resolution of ~1000. A preliminary reduction based on archival calibration
lamps, reveals the Mg II doublet plus several Fe II lines at a common
redshift of z = 1.21, which we identify as the redshift of the GRB.