[vsnet-grb-info 3132] GRB060418: Magellan/MIKE Spectroscopic Redshift

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4969
SUBJECT: GRB060418: Magellan/MIKE Spectroscopic Redshift
DATE:    06/04/18 05:04:41 GMT
FROM:    Hsiao-Wen Chen at U Chicago  <hchen at oddjob.uchicago.edu>

A. K. Dupree, E. Falco (Harvard-Smithsonian CfA), J. X. Prochaska 
(UCO/Lick Observatory), H.-W. Chen (U Chicago), and J. S. Bloom (UC 
Berkeley) report on behalf of the GRAASP collaboration:

"We observed the afterglow of GRB060418 reported by Falcone et al. (GCN 4966)
using the MIKE echelle spectrograph on the Magellan Clay telescope with a
0.7-arcsec slit.  The observations started at UT 03:34:02 on April 18, 2006,
~ 28 minutes after the inital Swift/BAT trigger.  The first exposure had a
total integration of 1200 sec under a mean seeing condition of 0.4 arcsec.
The mean signal-to-noise of the single exposure was S/N > 20 over the entire
3500 Ang to 9000 Ang spectral coverage.  We observed the strongest absorption
feaures at 6978 Ang and 6959 Ang, which we identify as the MgII absorption
doublet originated in the host of the GRB at z=1.49.  We therefore adopt
this as the redshift of the GRB host due to the absense of any other
absorption features beyond 7100 Ang.

Further analysis is underway.

This message may be cited."