TITLE:   GCN CIRCULAR
NUMBER:  7437
SUBJECT: GRB 080319B: Gemini-South Spectroscopy
DATE:    08/03/19 11:28:33 GMT
FROM:    Ryan Foley at UC Berkeley  <rfoley@astro.berkeley.edu>

R. J. Foley, D. Perley, and J. S. Bloom (UCB) on behalf of the GRAASP
collaboration report:

We obtained 2x1800 sec exposures of the optical afterglow (GCN 7428, 7430)
of GRB 080319B (GCN 7427) using GMOS on the Gemini-South telescope with
the R831 grating.  The observations started at 20080319.35 (~2 hours after
the initial Swift trigger).  Initial reductions show a featureless
continuum with no strong absorption systems, emission lines, or breaks.
Given our wavelength range of 595 - 815 nm, we can place the following
constraints on the redshift (in order of descending confidence):

(1) The lack of a Lyman limit implies z < 5.5.
(2) The lack of damped Lya or obvious Lya forest implies z < 3.9.
(3) The lack of obvious Mg II absorption implies z < 1.1.

Further analysis is in progress.