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GCN Circular 20180

GRB 161117A: VLT/X-shooter spectroscopy and redshift
2016-11-17T08:32:11Z (8 years ago)
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <>
Daniele Malesani (DARK/NBI and DTU Space), Thomas Kruehler (MPE), Kasper 
E. Heintz (Univ. Iceland and DARK/NBI), and Johan P. U. Fynbo (DARK/NBI) 
report on behalf of a larger collaboration:

We observed the optical afterglow of GRB 161117A (Cummings et al., GCN 
20179) with the ESO VLT Kueyen equipped with the X-shooter spectrograph. 
In the acquisition image, taken on 2016 Nov 17.097 UT (0.73 hr after the 
GRB), the optical afterglow is clearly detected with a magnitude R ~ 19 
(assuming R = 18.10 for the USNO star at RA = 21:28:14.70, Dec = 
-29:37:08.8). The seeing was very poor, around 2.5", and the sky 
conditions were partially cloudy.

Four spectra by 600 s each were collected covering the full X-shooter 
wavelength range 3000-25,000 AA. A faint trace is detected, down to at 
least 3800 ��. Superimposed on it, we are able to identify a number of 
absorption features which we interpret as due to Mg I, Mg II, and Fe II, 
all at a common redshift z = 1.549.

We acknowledge excellent support from the ESO observing staff in Paranal,
in particular Elizabeth Bartlett, Eleonora Sani, Steffen Mieske, and Jose
Velasquez, and the visiting astronomers Gerard Gilmore, Amelia Bayo, and
Aurora Aguayo.

[GCN OPS NOTE(17nov16):  Per author's request, the last paragraph was modified.]
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