Bright gamma-ray flares observed in GRB131108A

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 $\gamma$-ray flares dominating above 100 MeV, which are not directly related to the prompt emission in the GBM 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 $\gamma$-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 $\sim$ 2.0) $\times$ 10${}^{-6}$ erg cm${}^{-2}$, is comparable to that of emission during the steep decay phase, 1.7 $\times$ 10${}^{-6}$ erg cm${}^{-2}$. The total fluence from three $\gamma$-ray flares is 5.3 $\times$ 10${}^{-6}$ erg cm${}^{-2}$. The three $\gamma$-ray flares show properties similar to the usual X-ray flares that are sharp flux increases, occurring in $\sim$ 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 ($\alpha$ = 2 + $\beta$), which is the first observational evidence of the high-latitude emission in the GeV energy band.

arXiv commentApJL, 10 pages, 3 figures, 2 tables

References in corpus (34)

• Spectra and Light Curves of Gamma-Ray Burst Afterglows
• Optical and Long Wavelength Afterglow from Gamma-Ray Bursts
• Physical processes shaping GRB X-ray afterglow lightcurves: theoretical implications from the Swift XRT observations
• Evidence for a Canonical GRB Afterglow Light Curve in the Swift/XRT Data
• Bright X-ray Flares in Gamma-Ray Burst Afterglows
• Afterglow Emission from Naked Gamma-Ray Bursts
• The First Fermi LAT Gamma-Ray Burst Catalog
• Expanding Relativistic Shells and Gamma-Ray Burst Temporal Structure
• The First Survey of X-ray Flares from Gamma Ray Bursts Observed by Swift: Temporal Properties and Morphology
• A decade of Gamma-Ray Bursts observed by $Fermi$-LAT: The 2${}^{nd}$ GRB catalog
• External forward shock origin of high energy emission for three GRBs detected by Fermi
• GeV emission from Gamma Ray Bursts: a radiative fireball?
• Testing the Curvature Effect and Internal Origin of Gamma-Ray Burst Prompt Emissions and X-ray Flares with Swift Data
• Late internal shock model for bright X-ray flares in Gamma-ray Burst afterglows and GRB 011121
• The First Survey of X-ray Flares from Gamma Ray Bursts Observed by Swift: Spectral Properties and Energetics
• Unveiling the origin of X-ray flares in Gamma-Ray Bursts
• Variabilities of Gamma-Ray Burst Afterglows: Long-acting Engine, Anisotropic Jet or Many Fluctuating Regions?
• The Giant X-ray Flare of GRB 050502B: Evidence for Late-Time Internal Engine Activity
• High Energy Afterglow from Gamma-ray Bursts
• X-ray flare in XRF 050406: evidence for prolonged engine activity
• X-ray flares and the duration of engine activity in gamma-ray bursts
• The Onset of Gamma-Ray Burst Afterglow
• GeV-TeV and X-ray flares from gamma-ray bursts
• Towards a Better Understanding of the GRB Phenomenon: a New Model for GRB Prompt Emission and its effects on the New Non-Thermal L${}_{\mathrm{i}}^{\mathrm{NT}}$-E${}_{\mathrm{peak},\mathrm{i}}^{\mathrm{rest},\mathrm{NT}}$ relation
• GRB 060313: A New Paradigm for Short-Hard Bursts?
• Nearly Periodic Fluctuations in the Long Term X-ray Light Curves of the Blazars AO 0235+164 and 1ES 2321+419
• Is GeV Emission from Gamma-Ray Bursts of External Shock Origin?
• Detection of High-Energy Gamma-Ray Emission during the X-ray flaring activity in GRB100728A
• Prompt optical emission from residual collisions in GRB outflows
• Evidence of Bulk Acceleration of the GRB X-ray Flare Emission Region
• Closure relations of Gamma Ray Bursts in high energy emission
• High energy afterglows and flares from Gamma-Ray Burst by Inverse Compton emission
• Gamma-ray Burst Flares: X-ray Flaring. II
• A Statistical Study of GRB X-ray Flares: Evidence of Ubiquitous Bulk Acceleration in the Emission Region

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