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GCN Circular 13213

Subject
GRB 120404A: Gemini-N Redshift
Date
2012-04-04T15:17:07Z (12 years ago)
From
Antonino Cucchiara at UCSC/UCO Lick <acucchia@ucolick.org>
A. Cucchiara (UCSC/UCO Lick), on behalf of a larger
collaboration reports:

On April 4.58 UT (~60 minutes after the BAT trigger) 
we observed the field of GRB 120404A (Stratta et al., 
GCN 13208) using GMOS Spectrograph on the Gemini-North 
8-m telescope.  

The optical afterglow is clearly detected in our r-band 
acquisition image. 
We performed 2x900s spectroscopic observations of the 
optical afterglow using the B600 grating centered at 6500 
Angstrom (covering the range 5100-7900 A).
The spectrum reveals several absorption features, including 
FeII2586,2600, MgII2796,2803 at a common redshift of 1.633.
Other features indicate at least one MgII intervening system at
z=1.101

We therefore suggest that the redshift of GRB 120404A is z=1.633.

We thank the Gemini-North staff for their prompt support.
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