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GCN Circular 13441

Subject
GRB 120711A Gemini-S likely redshift
Date
2012-07-11T12:46:35Z (12 years ago)
From
Nial Tanvir at U.Leicester <nrt3@star.le.ac.uk>
N. R. Tanvir, K. Wiersema (U. Leicester), A. J. Levan (U. Warwick),
D. Fox (Penn State), A. Fruchter (STScI) and D. Krogsrud (Gemini)
report on behalf of a larger collaboration:

We observed the afterglow of GRB 120711A (Gotz et al. GCN 12434;
Lacluyze et al. GCN 12430) using the GMOS-S spectrograph on Gemini-South.

Observations began at 2012-7-11 10:08 UT, about 7.5 hr post-burst.
The data were obtained at high air-mass and on the boundary of twilight,
so the signal-to-noise is rather poor.  Nevertheless,
in the spectrum we identify lines of MgII (2797/2804A) and
FeII (2374/2383/2587/2600A) at a common redshift of z=1.405.

This therefore provides a robust lower-limit to the redshift of the GRB.
Furthermore, given the lack of other absorption features, in particular
any matching a redshift z~3 (Elliott et al. GCN 13438), we tentatively
identify z=1.405 as the most likely GRB redshift.
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