[vsnet-grb-info 6699] GRB080928: Gemini-South Absorption Redshift

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8300
SUBJECT: GRB080928: Gemini-South Absorption Redshift
DATE:    08/09/29 15:31:33 GMT
FROM:    Antonino Cucchiara at PSU  <cucchiara at astro.psu.edu>

A. Cucchiara, D. B. Fox (Penn State), S. B. Cenko  (Berkeley) and E. Berger
(Princeton) report on behalf of a larger collaboration:

Starting at 06:54 UT on 2008 September 29 (T0+16h) we observed the optical
counterpart of GRB 080928 (Sakamoto et al., GCN 8292, Rykoff  et al., 
GCN 8293)
using Gemini-South with the GMOS-South spectrograph (R~1200).
We acquired 2x900s spectra which covered the wavelength range 4000A-8000A.

Our spectrum shows a flux cut-off blueward of 4500A indicating a likely DLA
associated with the GRB host galaxy, consistent with a redshift of z ~ 2.6.

We also identify multiple metal absorption features including FeII(2249),
FeII(2260), SiIV(1393), SiIV(1402), CIV(1548), CIV(1550), NiII(1741) and
NiII(1751) at a common redshift of z = 2.49.

Therefore we conclude that GRB080928 occurred in a possible DLA galaxy
at z = 2.49.

We thank the Gemini staff for conducting these observations.