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, S.S.CovinoD'Elia, ValerioValerioD'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.PuglieseSánchez-Ramírez, R.R.Sánchez-RamírezSchulze, 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.Xu2020-09-172020-09-172018-09-01https://hdl.handle.net/20.500.13025/5539The Astrophysical Journal, Volume 865, Issue 2, article id. 107, 16 pp. (2018).Gamma-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}_-0.12^+0.06 from Very Large Telescope/X-shooter spectroscopy. At this redshift the peak 15 -150 keV luminosity of the burst was 3.2 × 10^52 erg s^-1, 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^-2 cm^-3 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}_jet≈ 5° . The beaming-corrected γ-ray energy is then {E}_ γ ≈ 2 ×{10}^50 erg, while the beaming-corrected kinetic energy is lower, {E}_{{K}}≈ {10}^49 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.dark agesreionizationfirst starsgalaxies: high-redshiftgamma-ray burst: generalgamma-ray burst: individual: GRB 120923Ajournal article10.3847/1538-4357/aadba9http://adsabs.harvard.edu/abs/2018ApJ...865..107Thttps://iopscience.iop.org/article/10.3847/1538-4357/aadba92018ApJ...865..107T