GRB 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) × 10-6 erg cm-2, is comparable to that of emission during the steep decay phase, 1.7 × 10-6 erg cm-2. The total fluence from three γ-ray flares is 5.3 × 10-6 erg cm-2. 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 (α = 2 + β ), which is the first observational evidence of the high-latitude emission in the GeV energy band.

Bright Gamma-Ray Flares Observed in GRB 131108A

Ajello M.;Baldini L.;Berretta A.;Bonino R.;Buson S.;Costantin D.;Fusco P.;Giglietto N.;Green D.;Loparco F.;Maldera S.;Piron F.;
2019

Abstract

GRB 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) × 10-6 erg cm-2, is comparable to that of emission during the steep decay phase, 1.7 × 10-6 erg cm-2. The total fluence from three γ-ray flares is 5.3 × 10-6 erg cm-2. 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 (α = 2 + β ), which is the first observational evidence of the high-latitude emission in the GeV energy band.
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https://arxiv.org/abs/1911.04642
Ajello M.; Arimoto M.; Asano K.; Axelsson M.; Baldini L.; Barbiellini G.; Bastieri D.; Bellazzini R.; Berretta A.; Bissaldi E.; Blandford R.D.; Bonino R.; Bottacini E.; Bregeon J.; Bruel P.; Buehler R.; Buson S.; Cameron R.A.; Caputo R.; Caraveo P.A.; Cavazzuti E.; Chen S.; Chiaro G.; Ciprini S.; Costantin D.; Cutini S.; D'Ammando F.; Torre Luque P.D.L.; Palma F.D.; Lalla N.D.; Venere L.D.; Dirirsa F.F.; 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.; Hays E.; Horan D.; Johannesson 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.; Marti-Devesa G.; Mazziotta M.N.; McEnery J.E.; Mereu I.; Michelson P.F.; Mizuno T.; 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.; Raino S.; Rando R.; Rani B.; Razzano M.; Reimer A.; Reimer O.; Serini D.; Sgro C.; Siskind E.J.; Spandre G.; Spinelli P.; Tajima H.; Takagi K.; Tak D.; Torres D.F.; Valverde J.; Wood K.; Yamazaki R.; Yassine M.; Zhu S.; Uhm Z.L.; Zhang B.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/1744108
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