GCN Circular 5002
Subject
GRB060418: Further Analysis of MIKE Spectroscopy
Date
2006-04-24T17:27:34Z (18 years ago)
From
Jason Prochaska at UCO/Lick Obs <xavier@ucolick.org>
J. X. Prochaska (UCO/Lick Observatory), H.-W. Chen (U Chicago), J. S.
Bloom (UC
Berkeley), E. Falco, and A. K. Dupree (Harvard-Smithsonian CfA)
report on behalf of the
GRAASP collaboration:
"We have further analyzed the echelle spectra of GRB060418 (Falcone
et al.
GCN 4966), obtained using MIKE on the Magellan Clay telescope (Dupree
et al.
GCN 4969). We report the detection of ZnII, SiII, SiII*, FeII, FeII*,
MgII, MgI, AlIII, CIV and NiII transitions among others at a redshift
z=1.4901 +/- 0.0001. The relative populations of the excited
FeII levels are similar to GRB051111 (PHB06, astro-ph/0601057); the
J=7/2 to
J=1/2 states follow a Boltzmann distribution with T=1000-5000K.
But, following GRB051111 and GRB050730, we interpret the FeII excitation
as the result of indirect UV pumping by the GRB afterglow. The
detection
of strong MgI absorption places this gas (and presumably the majority of
low-ion gas) at a distance r>50pc from the GRB. Finally, we measure
[Si/Fe]=+0.5dex indicating a modest dust-to-metals ratio.
This message may be cited."