Ajello, M.M.AjelloArimoto, M.M.ArimotoAsano, K.K.AsanoAxelsson, M.M.AxelssonBaldini, L.L.BaldiniBarbiellini, G.G.BarbielliniBastieri, D.D.BastieriBellazzini, R.R.BellazziniBerretta, A.A.BerrettaBissaldi, E.E.BissaldiBlandford, R. D.R. D.BlandfordTajima, H.H.TajimaTakagi, K.K.TakagiTak, D.D.TakTorres, D. F.D. F.TorresValverde, J.J.ValverdeWood, K.K.WoodYamazaki, R.R.YamazakiYassine, M.M.YassineZhu, S.S.ZhuUhm, Z. LucasZ. LucasUhmBonino, R.R.BoninoZhang, BingBingZhangBottacini, E.E.BottaciniBregeon, J.J.BregeonBruel, P.P.BruelBuehler, R.R.BuehlerBuson, S.S.BusonCameron, R. A.R. A.CameronCaputo, R.R.CaputoCaraveo, P. A.P. A.CaraveoCavazzuti, E.E.CavazzutiChen, S.S.ChenChiaro, G.G.ChiaroCiprini, S.S.CipriniCostantin, D.D.CostantinCutini, S.S.CutiniD'AMMANDO, FILIPPOFILIPPOD'AMMANDOde la Torre Luque, P.P.de la Torre Luquede Palma, F.F.de PalmaDi Lalla, N.N.Di LallaDi Venere, L.L.Di VenereFana Dirirsa, F.F.Fana DirirsaFegan, S. J.S. J.FeganFranckowiak, A.A.FranckowiakFukazawa, Y.Y.FukazawaFusco, P.P.FuscoGargano, F.F.GarganoGasparrini, D.D.GasparriniGiglietto, N.N.GigliettoGiordano, F.F.GiordanoGIROLETTI, MARCELLOMARCELLOGIROLETTIGreen, D.D.GreenGrenier, I. A.I. A.GrenierGrondin, M. -H.M. -H.GrondinGuiriec, S.S.GuiriecHays, E.E.HaysHoran, D.D.HoranJóhannesson, G.G.JóhannessonKocevski, D.D.KocevskiKovac'evic', M.M.Kovac'evic'Kuss, M.M.KussLarsson, S.S.LarssonLatronico, L.L.LatronicoLi, J.J.LiLiodakis, I.I.LiodakisLongo, F.F.LongoLoparco, F.F.LoparcoLovellette, M. N.M. N.LovelletteLubrano, P.P.LubranoMaldera, S.S.MalderaManfreda, A.A.ManfredaMartí-Devesa, G.G.Martí-DevesaMazziotta, M. N.M. N.MazziottaMcEnery, J. E.J. E.McEneryMereu, I.I.MereuMichelson, P. F.P. F.MichelsonMizuno, T.T.MizunoMonzani, M. E.M. E.MonzaniMoretti, E.E.MorettiMorselli, A.A.MorselliMoskalenko, I. V.I. V.MoskalenkoNegro, M.M.NegroNuss, E.E.NussOhno, M.M.OhnoOmodei, N.N.OmodeiORIENTI, MonicaMonicaORIENTIOrlando, E.E.OrlandoPalatiello, M.M.PalatielloPaliya, V. S.V. S.PaliyaPaneque, D.D.PanequePei, Z.Z.PeiPERSIC, MassimoMassimoPERSICPesce-Rollins, M.M.Pesce-RollinsPetrosian, V.V.PetrosianPiron, F.F.PironPoon, H.H.PoonPorter, T. A.T. A.PorterPrincipe, G.G.PrincipeRacusin, J. L.J. L.RacusinRainò, S.S.RainòRando, R.R.RandoRani, B.B.RaniRazzano, M.M.RazzanoReimer, A.A.ReimerReimer, O.O.ReimerSerini, D.D.SeriniSgrò, C.C.SgròSiskind, E. J.E. J.SiskindSpandre, G.G.SpandreSpinelli, P.P.Spinelli2021-01-272021-01-2720192041-8205http://hdl.handle.net/20.500.12386/30034GRB 131108A is a bright long gamma-ray burst (GRB) detected by the Large Area Telescope and the Gamma-ray Burst Monitor on board the Fermi Gamma-ray Space Telescope. Dedicated temporal and spectral analyses reveal three γ-ray flares dominating above 100 MeV, which are not directly related to the prompt emission in the Gamma-ray Burst Monitor band (10 keV-10 MeV). The high-energy light curve of GRB 131108A (100 MeV-10 GeV) shows an unusual evolution: a steep decay, followed by three flares with an underlying emission, and then a long-lasting decay phase. The detailed analysis of the γ-ray flares finds that the three flares are 6-20 times brighter than the underlying emission and are similar to each other. The fluence of each flare, (1.6 ∼ 2.0) × 10<SUP>-6</SUP> erg cm<SUP>-2</SUP>, is comparable to that of emission during the steep decay phase, 1.7 × 10<SUP>-6</SUP> erg cm<SUP>-2</SUP>. The total fluence from three γ-ray flares is 5.3 × 10<SUP>-6</SUP> erg cm<SUP>-2</SUP>. The three γ-ray flares show properties similar to the usual X-ray flares that are sharp flux increases, occurring in ∼50% of afterglows, in some cases well after the prompt emission. Also, the temporal and spectral indices during the early steep decay phase and the decaying phase of each flare show the consistency with a relation of the curvature effect (\hat{α } = 2 + \hat{β }), which is the first observational evidence of the high-latitude emission in the GeV energy band.STAMPAenArticle10.3847/2041-8213/ab564f2-s2.0-85077649318000499346800001https://iopscience.iop.org/article/10.3847/2041-8213/ab564f2019ApJ...886L..33AFIS/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