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GCN Circular 13890

GRB 121024A: VLT/X-shooter redshift
2012-10-24T07:10:59Z (11 years ago)
Nial Tanvir at U.Leicester <>
N. R. Tanvir (U. Leicester), J. P. U. Fynbo (DARK/NBI), A. Melandri (INAF-OAB), 
A. J. Levan (U. Warwick), D. Xu (WIS), V. D'Elia (ASDC) report on behalf of 
the X-shooter GTO collaboration:

We observed the afterglow of GRB 121024A (Pagani et al. GCN 13886) with the
X-shooter spectrograph at the VLT. Observations began at 04:45 UT, approximately
1.8 hours after the initial detection of the burst. The afterglow is well detected in
the acquisition image, and in the resulting spectrum we see a strong, broad 
damped-Lya absorption feature at ~4000A, combined with numerous narrow metal 
lines of CIV, SiII, SiIV, FeII, SII and AlII, as well as fine-structure lines associated 
with SiII*. These point to a common redshift of z=2.298 for GRB 121024A.

We thank Maja Vuckovic, Giovanni Carraro, Marcelo Lopez and Felipe Gaete
for their assistance in obtaining these observations, and Gianni Marconi
and Gerry Gilmore for kindly allowing the ToO to be performed during their
visitor mode run.
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