A. Cucchiara (NASA/GSFC) reports on behalf of a larger collaboration:
We obtained a spectrum of the afterglow (Kennea et al., GCN 16978, Gorbovskoy et al.
GCN 16972, Graham et al. GCN 16977, Siegel et al. GCN 16979) of the Fermi GRB 141028A
(Bissaldi et al., GCN 16969, Roberts et al. GCN 16971) with the Gemini Multi-Object
Spectrograph mounted on the 8 m Gemini-North telescope.
Observations began at 05:07 UT on 2014 October 29 (~18. hr after the Fermi-GBM trigger)
and cover the wavelength range from 3800-8200 A. We acquired 2x600s exposure
using the R400 grism.
We detect several absorption lines, including CrII2056,ZnII2056, FeII2260, FeII2344,
FeII2586, FeII2600, MgII2706, MgII2803, and MgI 2853 at the common redshift of z=1.82.
We therefore suggest this to be the redshift of GRB 141028A.
We thank the Gemini-North staff for their terrific support, in particular
A. Petric and A. Smith.