Tanvir, N. R.N. R.TanvirLaskar, T.T.LaskarLevan, A. J.A. J.LevanPerley, D. A.D. A.PerleyZabl, J.J.ZablFynbo, J. P. U.J. P. U.FynboRhoads, J.J.RhoadsCenko, S. B.S. B.CenkoGreiner, J.J.GreinerWiersema, K.K.WiersemaHjorth, J.J.HjorthCucchiara, A.A.CucchiaraBerger, E.E.BergerBremer, M. N.M. N.BremerCano, Z.Z.CanoCobb, B. E.B. E.CobbCOVINO, StefanoStefanoCOVINOD'Elia, V.V.D'EliaFong, W.W.FongFruchter, A. S.A. S.FruchterGoldoni, P.P.GoldoniHammer, F.F.HammerHeintz, K. E.K. E.HeintzJakobsson, P.P.JakobssonKann, D. A.D. A.KannKaper, L.L.KaperKlose, S.S.KloseKnust, F.F.KnustKrühler, T.T.KrühlerMalesani, D.D.MalesaniMisra, K.K.MisraNicuesa Guelbenzu, A.A.Nicuesa GuelbenzuPugliese, G.G.PuglieseSANCHEZ RAMIREZ, RUBENRUBENSANCHEZ RAMIREZSchulze, S.S.SchulzeStanway, E. R.E. R.Stanwayde Ugarte Postigo, A.A.de Ugarte PostigoWatson, D.D.WatsonWijers, R. A. M. J.R. A. M. J.WijersXu, D.D.Xu2020-10-122020-10-1220180004-637Xhttp://hdl.handle.net/20.500.12386/27727Gamma-ray bursts (GRBs) are powerful probes of early stars and galaxies, during and potentially even before the era of reionization. Although the number of GRBs identified at z ≳ 6 remains small, they provide a unique window on typical star-forming galaxies at that time, and thus are complementary to deep field observations. We report the identification of the optical drop-out afterglow of Swift GRB 120923A in near-infrared Gemini-North imaging, and derive a redshift of z={7.84}<SUB>-0.12</SUB><SUP>+0.06</SUP> from Very Large Telescope/X-shooter spectroscopy. At this redshift the peak 15-150 keV luminosity of the burst was 3.2 × 10<SUP>52</SUP> erg s<SUP>-1</SUP>, and in this sense it was a rather typical long-duration GRB in terms of rest frame luminosity. This burst was close to the Swift/Burst Alert Telescope detection threshold, and the X-ray and near-infrared afterglow were also faint. We present ground- and space-based follow-up observations spanning from X-ray to radio, and find that a standard external shock model with a constant-density circumburst environment of density n ≈ 4 × 10<SUP>-2</SUP> cm<SUP>-3</SUP> gives a good fit to the data. The near-infrared light curve exhibits a sharp break at t ≈ 3.4 days in the observer frame which, if interpreted as being due to a jet, corresponds to an opening angle of {θ }<SUB>jet</SUB>}≈ 5^\circ . The beaming-corrected γ-ray energy is then {E}<SUB>γ </SUB>≈ 2× {10}<SUP>50</SUP> erg, while the beaming-corrected kinetic energy is lower, {E}<SUB>{{K</SUB>}}≈ {10}<SUP>49</SUP> erg, suggesting that GRB 120923A was a comparatively low kinetic energy event. We discuss the implications of this event for our understanding of the high-redshift population of GRBs and their identification.STAMPAenArticle10.3847/1538-4357/aadba92-s2.0-85054848197000445964000007https://iopscience.iop.org/article/10.3847/1538-4357/aadba92018ApJ...865..107TFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation::PE9_6 Stars and stellar systems