[vsnet-grb-info 12700] GRB 121211A: Keck/LRIS redshift

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14059
SUBJECT: GRB 121211A: Keck/LRIS redshift
DATE:    12/12/11 18:38:05 GMT
FROM:    Daniel Perley at Caltech  <dperley at astro.caltech.edu>

D. A. Perley (Caltech), J. X. Prochaska (UCO/Lick), and A. N. Morgan (UC 
Berkeley) report:

We slewed with the Keck I telescope (+LRIS) to the location of GRB 
121211A (Mangano et al., GCN 14057) immediately following the GCN 
notice.   The optical transient (Mangano et al.; Japelj et al., GCN 
14058) was identified on the guider camera and longslit exposures began 
at 14:01 UT, 14 minutes after the GRB trigger.  After a single short 
observation in low resolution we acquired 2x860s exposures on the blue 
and red side.  The spectral range extends from 3150-5630 and 5790-7440 
Angstroms.

We identify FeII (2344, 2374, 2382, 2586, 2600) and possible FeII* and 
MnII at a redshift of z=1.023, as well as a marginal detection of MgII 
(2796, 2804) at the same redshift using the short initial exposure, 
which covers the dichroic gap.   We suggest this as the redshift of GRB 
121211A.