TITLE:   GCN CIRCULAR
NUMBER:  18487
SUBJECT: GRB 151027A: Keck/HIRES redshift
DATE:    15/10/27 13:57:31 GMT
FROM:    Daniel Perley at Caltech  <dperley@astro.caltech.edu>

D. A. Perley (DARK/NBI), L. Hillenbrand (Caltech), and J. X. Prochaska 
(UCO/Lick) report:

We obtained a 900s spectrum of the optical afterglow of GRB 151027A 
(Maselli et al., GCN 18478) with Keck/HIRES starting at UT 06:54 on 
2015-10-27.  In the preliminary reduction, we identify a series of 
strong absorption lines including the MgII doublet at z=0.81. Associated 
MgI, FeII, and (likely) FeII* are also present, indicating that this is 
the redshift of the GRB.  Analysis is ongoing.