GCN Circular 23710

D. A. Kann, C. C. Thoene (both HETH/IAA-CSIC), J. Selsing 
(DAWN/NBI/DTU), L. Izzo (HETH/IAA-CSIC), A. de Ugarte Postigo 
(HETH/IAA-CSIC and DARK/NBI), G. Pugliese (API, Univ. Amsterdam), B. 
Sbarufatti (PSU), K. E. Heintz (Univ. Iceland), V. D'Elia (ASI/SSDC, 
INAF/OAR), S. Covino (INAF-OAB), K. Wiersema (Univ. Warwick), D. A. 
Perley (LJMU), S. Vergani (GEPI/Obs. Paris), J. P. U. Fynbo 
(DAWN/NBI/DTU), D. Watson (DAWN/NBI), N. R. Tanvir (Univ. Leicester), D. 
Hartmann (Clemson Univ.), D. Xu (NAOC), S. Schulze (WIS), and J. Bolmer 
(MPE) report on behalf of the Stargate Consortium:

We observed the optical counterpart of GRB 190114C (Gropp et al., GCN 
#23688; Tyurina et al., GCN #23690; Lipunov et al., GCN #23693; Selsing 
et al., GCN #23695; Izzo et al., GCN #23699; Bolmer & Schady, GCN 
#23702), the first-ever TeV-detected GRB (Mirzoyan et al., GCN #23701), 
with the ESO-VLT UT2 (Kueyen) equipped with the X-shooter spectrograph, 
covering the wavelength range 3000-21000 AA. We acquired four 600 second 
spectra on 2019-01-15 between 01:42UT and 02:32UT, approximately 4.75 
hours after the GRB. In the acquisition image we measure r' = 18.2 +/- 
0.4 (AB), calibrated against several nearby Pan-STARRS comparison stars.

We detect several strong absorption features, namely Ca H&K, Na ID, Mg 
II and Mg I, at a common redshift z = 0.4250, consistent with the values 
reported by Selsing et al. (GCN #23695) and Castro-Tirado et al. (GCN 
#2370, and in agreement with the existence of a likely host galaxy in 
archival observations (de Ugarte Postigo et al., GCN #23692). 
Furthermore, the spectrum shows OII, Hbeta, OIII and Halpha in emission 
at the same redshift, fully confirming it.

The line-of-sight is highly extinguished, which is in agreement with the 
large column density seen in Swift XRT observations (Evans et al., GCN 
#23706) as well as the red GROND colors (Bolmer & Schady, GCN #23702).

We acknowledge Bin Yang, Elizabeth Bartlett, Trystyn Berg, and Juan 
Carlos Olivares at Paranal for their excellent help in obtaining these 
observations.