[vsnet-grb-info 8592] GRB 091029: Gemini-South Redshift

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  10100
SUBJECT: GRB 091029: Gemini-South Redshift
DATE:    09/10/29 07:49:19 GMT
FROM:    Ryan Chornock at UC Berkeley  <chornock at astro.berkeley.edu>

R. Chornock, D. A. Perley, and B. E. Cobb (UC Berkeley) report on behalf of a
larger collaboration:

We obtained optical spectra of the afterglow of GRB 091029 (Grupe et al., GCN
10097; Filgas et al., GCN 10098; LaCluyze et al., GCN 10099) using GMOS on
Gemini-South.  Our spectra cover the wavelength range of 3900-8100 angstroms
with the R400 grating.  Our first 600s exposure, starting at 06:06 UT on Oct. 29
(2.2 hr after the BAT trigger) reveals absorption lines from Lyman-alpha, C II,
C IV, Si II, and Si IV at a common redshift of 2.752, which we identify as
the redshift of the GRB.  The afterglow is still quite bright (R~17.8 mag at
t=2.02 hr) in the acquisition image.

We would like to thank German Gimeno and the Gemini staff for their assistance.