[vsnet-grb-info 2132] GRB 050908: DEIMOS spectrum and further analysis

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3971
SUBJECT: GRB 050908: DEIMOS spectrum and further analysis 
DATE:    05/09/12 17:39:33 GMT
FROM:    Jason Prochaska at UCO/Lick Obs  <xavier at ucolick.org>

J. X. Prochaska (UCO-Lick/UCSC), R. J. Foley (UCB), H.-W. Chen
(U Chichago), J. S. Bloom (UCB), K. Hurley (SSL/UCB), M. Cooper (UCB),
R. Guhathakurta (UCO-Lick/UCSC), W. Li (UCB) report on behalf of the
GRAASP collaboration:

"We have obtained Keck/DEIMOS spectra of the afterglow of 050908  
starting
at 20050908.56 UT.  The 1200/7500 grating data has a resolution of ~0.33
Ang and S/N~10 per resolution element covering wavelengths 6300-9000  
Ang.
We refine the GRB host redshift to be z=3.3440 +/- 0.0001 based on the
strongest component of the CIV profile.

The DEIMOS spectrum overlaps with GMOS spectrum between 6330 and 7950 A,
and does not confirm the emission feature originally detected in the  
GMOS
data at 7273 A.  We therefore conclude that the intervening system at
z=2.81 reported in GCN 3949 is not likely to be real.

Adopting log N(HI)=19 and ignoring ionization corrections, the
non-detections of CII 1334, OI 1302 and AlII 1670 imply a metallicity of
less than 1/100 solar.  Ionization corrections could imply even 10x  
lower
values.

In contrast to the low-ion transitions, the host shows very strong SiIV
and CIV absorption spanning ~500 km/s."

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