[vsnet-grb-info 18955] GRB 170113A: VLT/X-shooter redshift

[GCN Circulars]

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  <dxu at nao.cas.cn>

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.