A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), D. A. Kann (TLS Tautenburg),
C. Thoene (IAA-CSIC), L. Izzo (IAA-CSIC), R. Sanchez-Ramirez (IAA-CSIC),
Z. Cano (IAA-CSIC), K. Bensch (IAA-CSIC), D. Garcia-Alvarez (IAC, ULL,
GRANTECAN) and D. Perez Valladares (GRANTECAN) report :
We observed the afterglow of GRB 161017A (Yurkov et al., GCN 20063,
Troja et al. GCN 20064) with OSIRIS at the 10.4m GTC telescope on
La Palma (Spain). The observations started at 04:38:44 UT (10.78 hr after
the burst) and consist of 3 x 900 s spectra using grism R1000B, which
covers the spectral region between 3700 and 7800 AA at a resolution of
R ~ 1000.
The r-band acquisition image shows the afterglow at a magnitude of r(AB) =
18.24+/-0.07, as compared to several SDSS stars.
The spectrum shows a strong continuum with weak features of SiII, CIV, AlII,
and FeII at a common redshift of 2.013, which we identify as the redshift of the
GRB. Additionally, we detect two intervening systems at z=0.916 and z=1.370,
both with MgII features.