GCN Circular 19274

J. Selsing (DARK/NBI), P.M. Vreeswijk (WIS), J. Japelj (INAF/OATs), V. 
D'Elia (ASI/ASDC and INAF/Roma), A. de Ugarte Postigo (IAA/CSIC and 
DARK/NBI), G. Pugliese (API/UvA), D. Xu (NAOC/CAS), D. Malesani 
(DARK/NBI), T. Kruehler (MPE), J.P.U. Fynbo (DARK/NBI), report on behalf 
of a larger collaboration:

We observed the optical afterglow of GRB 160410A (Gibson et al., GCN 
19271
Not found
 
 
; Yates et al., GCN 19272
Not found
 
 
) with the ESO Very Large Telescope UT2 
(Kueyen) equipped with X-shooter. Observations were triggered 
robotically in "rapid response mode" (RRM). Our spectroscopic 
integration started 8.4 min after the GRB and 3x600 s spectra were 
collected covering the wavelength range 3000-24,500 AA, until the target 
became too low on the horizon.

The optical afterglow is detected in our acquisition image (7.7 min 
after the GRB) with a magnitude r = 20.29 +- 0.06 (AB), calibrated 
against two nearby SDSS stars.

Our spectra reveal continuum over the entire spectral range redward of 
~3400 AA, which constrains the redshift to be z < 1.8. Besides, a number 
of weak absorption features are detected, which we interpret as due to 
Fe II and Al II at a redshift z = 1.717. At this redshift, the Mg II 
2796,2803 doublet lies into a region of strong telluric absorption (the 
A band) and is not detected. Two intervening C IV absorbers are also 
observed at z = 1.444 and z = 1.581.

We acknowledge excellent and prompt support from the ESO staff at 
Paranal, in particular Annalisa De Cia and Cedric Ledoux.