[vsnet-grb-info 15071] GRB 140606B / Fermi 432717114 / iPTF 14bfu: Keck redshift

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16365
SUBJECT: GRB 140606B / Fermi 432717114 / iPTF 14bfu: Keck redshift
DATE:    14/06/08 02:09:34 GMT
FROM:    Daniel Perley at Caltech  <dperley at astro.caltech.edu>

D. A. Perley, Y. Cao (Caltech), M. Kasliwal (Carnegie), and E. Kirby 
(UCI) report:

On the night of 2014-06-07 starting at 19:16 (UT) we acquired two 900 
second optical spectra of iPTF14bfu (Singer et al., GCN 16360), an 
optical transient in the error circle of GRB 140606B / Fermi 432717114 
(Burns et al., GCN 16360), with the DEIMOS spectrograph on the Keck II 
10 meter telescope.

In the reduced spectrum of this object we identify emission lines from 
OII, OIII (5007) and H-alpha, as well as absorption features from Ca II 
(H+K), at a consistent redshift of z = 0.384.  A serendipitous galaxy 
offset by ~2 arcseconds (10 kpc) along the slit shows the same emission 
lines at identical redshift but no detectable continuum.

Given this redshift, the high luminosity inferred for the optical 
transient at the time of the initial detection (absolute magnitude ~ 
-21.7) favors the association of this source as the optical afterglow of 
GRB 140606B.