TITLE: GCN CIRCULAR NUMBER: 20458 SUBJECT: GRB 170113A: VLT/X-shooter redshift DATE: 17/01/14 17:33:08 GMT FROM: Dong Xu at NAOC/CAS D. Xu (NAOC/CAS), K. E. Heintz (Univ. Iceland and DARK/NBI), D. Malesani, J. P. U. Fynbo (DARK/NBI) report on behalf of a larger collaboration: We observed the optical afterglow of GRB 170113A (Evans et al. GCN 20446; Veres et al., GCN 20452; Guidorzi et al., GCN 20448) with the ESO Very Large Telescope UT 2 (Kueyen) equipped with the X-shooter spectrograph, covering the wavelength range 3500-20000 AA. Spectroscopy started at 01:17:53 UT on 2017-01-14 (i.e., 15.23 hr after the GRB) and consisted of 4 exposures of 1200 s each. From the acquisition image prior to the spectroscopy, the afterglow has m(r)~21.7 mag, calibrated with nearby USNO B1 stars. The spectrum exhibits several absorption features such as Si II, Fe II, Mg II, as well as emission features such as [O II] doublet, Hbeta, [OIII] doublet, all at a common redshift of z=1.968. We conclude this is the redshift of the GRB. We acknowledge the excellent support from the ESO staff, particularly Luca Sbordone, Laura Magrini, Cedric Ledoux, and Elizabeth (Liz) Bartlett, in obtaining these observations.