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Arimoto, M.; Asano, K.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Bellazzini, R.; Berretta, A.; Blandford, R. D.; Bonino, R.; Bottacini, E.; Bregeon, J.; Bruel, P.; Buehler, R.; Buson, S.; Cameron, R. A.; Caputo, R.; Chen, S.; Ciprini, S.; Costantin, D.; Cutini, S.; D’Ammando, F.; Torre Luque, P. De La; Palma, F. De; Lalla, N. Di; Venere, L. Di; Dirirsa, F. Fana; Fegan, S. J.; Franckowiak, A.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Giglietto, N.; Giordano, F.; Giroletti, M.; Green, D.; Grenier, I. A.; Grondin, M.-H.; Guiriec, S.; Horan, D.; Jóhannesson, G.; Kocevski, D.; Kovac’evic’, M.; Kuss, M.; Larsson, S.; Latronico, L.; Li, J.; Liodakis, I.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Maldera, S.; Manfreda, A.; Martí-Devesa, G.; Mazziotta, M. N.; McEnery, J. E.; Mereu, I.; Michelson, P. F.; Monzani, M. E.; Moretti, E.; Morselli, A.; Moskalenko, I. V.; Negro, M.; Nuss, E.; Ohno, M.; Omodei, N.; Orienti, M.; Orlando, E.; Palatiello, M.; Paliya, V. S.; Paneque, D.; Pei, Z.; Persic, M.; Pesce-Rollins, M.; Petrosian, V.; Piron, F.; Poon, H.; Porter, T. A.; Principe, G.; Racusin, J. L.; Rainò, S.; Rando, R.; Rani, B.; Razzano, M.; Reimer, A.; Reimer, O.; Sgrò, C.; Siskind, E. J.; Spandre, G.; Spinelli, P.; Tajima, H.; Takagi, K.; Tak, D.; Torres, D. F.; Valverde, J.; Wood, K.; Yamazaki, R.; Zhu, S.; Zhang, Bing
2019Report
GRB 131108A is a bright long gamma-ray burst (GRB) detected by the Large Area Telescope and the Gamma-rayBurst Monitor on board the Fermi Gamma-ray Space Telescope. Dedicated temporal and spectral analyses revealthree γ-ray flares dominating above 100 MeV, which are not directly related to the prompt emission in the GammarayBurst 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 longlastingdecay phase. The detailed analysis of the γ-ray flares finds that the three flares are 6–20 times brighter thanthe underlying emission and are similar to each other. The fluence of each flare, (1.6∼2.0)×10−6 erg cm−2, iscomparable to that of emission during the steep decay phase, 1.7×10−6 erg cm−2. The total fluence from threeγ-ray flares is 5.3×10−6 erg cm−2. The three γ-ray flares show properties similar to the usual X-ray flares thatare sharp flux increases, occurring in ∼50% of afterglows, in some cases well after the prompt emission. Also, thetemporal and spectral indices during the early steep decay phase and the decaying phase of each flare show theconsistency with a relation of the curvature effect (aˆ =2 + bˆ ), which is the first observational evidence ofthe high-latitude emission in the GeV energy band.
