[vsnet-grb-info 1893] GRB 050730: Preliminary Analysis of MIKE Spectrum

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3732
SUBJECT: GRB 050730: Preliminary Analysis of MIKE Spectrum 
DATE:    05/08/02 06:00:34 GMT
FROM:    Jason Prochaska at UCO/Lick Obs  <xavier at ucolick.org>

J. X. Prochaska (UCO/Lick),  H.-W. Chen (MIT), J. S. Bloom (UCB),
J. O'Meara (MIT), S. M. Burles (MIT), I. Thompson (OCIW)
report on behalf of the GRAASP collaboration:

"We have performed preliminary analysis of our MIKE spectrum of
the afterglow of GRB 050730.  A profile fit to the Lya and Lyb
absorption lines of the sightline through the host galaxy gives
N(HI) = 22.15 +/- 0.05.  The simple and narrow metal-line profiles
give a redshift z=3.96855 +/- 0.00005. We estimate a neutral gas
metallicity of S/H ~ 1/100 solar which is lower than the
mean metallicity of damped Lya system at this redshift.  More  
strikingly,
we identify fine-structure lines of SiII*, OI*, OI**, and FeII*, the
majority of which are saturated.  Also, we identify absorption
features near 6150A which we interpret as the NV absorption doublet.

Finally, we identify an intervening damped Lya system at
z=3.5650 +/- 0.0001 with log N(HI)= 20.30 +/- 0.15 and low metallicity
as well as a z=1.773 MgII absorber.

A full analysis is underway.

Figures can be found at this following site:
    http://www.graasp.org/Data/index.html