N. R. Tanvir (U. Leicester), D. Fox (Penn State), J. Fynbo (DARK)
and C. Trujllo (Gemini) report on behalf of a larger collaboration:
We observed the afterglow of GRB 120802A (Holland et al. GCN 13555)
using the GMOS-N spectrograph on Gemini-North, covering a spectral
range of about 5900A to 10000A.
Observations began at 2012-8-2 13:30 UT, about 5:30 hr post-burst.
The spectrum reveals many absorption lines including S II (1250),
Si II (1260/1304/1526/1808), O I (1304), C II (1334), Si IV (1394/1403),
C IV (1548/1551), Fe II (1608), Al II (1670) at a common redshift of z=3.796,
which we believe is most likely the redshift of this burst. We no clear
evidence of any fine-structure lines.
Note, this redshift is consistent with the absence of a strong Lyman-alpha line or
Lyman-alpha forest since they would just fall off the blue end of our spectrum.
We also detect an intervening system at z=2.38, based on Fe II and Mg II features.