Observation of inverse Compton emission from a long γ-ray burst by Veres, P, Bhat, PN, Briggs, MS, Cleveland, WH, Hamburg, R, Hui, CM, Mailyan, B, Preece, RD, Roberts, OJ, von Kienlin, A, Wilson-Hodge, CA, Kocevski, D, Arimoto, M, Tak, D, Asano, K, Axelsson, M, Barbiellini, G, Bissaldi, E, Dirirsa, FF, Gill, R, Granot, J, McEnery, J, Omodei, N, Razzaque, S, Piron, F, Racusin, JL, Thompson, DJ, Campana, S, Bernardini, MG, Kuin, NPM, Siegel, MH, Cenko, SB, O'Brien, P, Capalbi, M, Daì, A, De Pasquale, M, Gropp, J, Klingler, N, Osborne, JP, Perri, M, Starling, RLC, Tagliaferri, G, Tohuvavohu, A, Ursi, A, Tavani, M, Cardillo, M, Casentini, C, Piano, G, Heywood, I, MAGIC Collaboration