GCN Circular 6890

Jason X. Prochaska (UCSC), D. A. Perley, M. Modjaz, J.S. Bloom,
D. Poznanski (UC Berkeley), and C.C. Thoene (Dark Cosmology Center)
report on behalf of GRAASP:

"We observed the afterglow of GRB 071010B with the Keck/LRIS
dual spectrometer for a series of 300s exposures starting
at UT 15:08 under good conditions.  We confirm the report
of Cenko et al. (GCN 6888
Not found
 
 
) of a strong MgII absorber at
z=0.947 in the afterglow spectrum.   Our data show corresponding
FeII transitions at rest-frame wavelengths: 2344, 2382, 2586,
and 2600.  We do not identify any FeII* transitions and also set
an upper limit to the rest equivalent width of ZnII 2026: EW<0.4A.
Such weak ZnII 2026 absorption is rare for GRB host galaxies,
but not unprecedented.

A more conservative upper limit to the GRB redshift
is set by the absence of IGM signatures at 3500A which
indicates z_GRB < 1.9.

Further analysis is in progress."


This GCN may be cited.

[GCN OPS NOTE(11oct07): Per the author's request, CCT was added
to the list of authors.]