GCN Circular 20458
Subject
GRB 170113A: VLT/X-shooter redshift
Date
2017-01-14T17:33:08Z (7 years ago)
From
Dong Xu at NAOC/CAS <dxu@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.