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Swift and Fermi Observations of X-Ray Flares: The Case of Late Internal ShockSimultaneous Swift and Fermi observations of gamma-ray bursts (GRBs) offer a unique broadband view of their afterglow emission, spanning more than 10 decades in energy. We present the sample of X-ray flares observed by both Swift and Fermi during the first three years of Fermi operations. While bright in the X-ray band, X-ray flares are often undetected at lower (optical), and higher (MeV to GeV) energies. We show that this disfavors synchrotron self-Compton processes as the origin of the observed X-ray emission. We compare the broadband properties of X-ray flares with the standard late internal shock model, and find that in this scenario, X-ray flares can be produced by a late-time relativistic (gamma greater than 50) outflow at radii R approximately 10(exp 13) - 10(exp 14) cm. This conclusion holds only if the variability timescale is significantly shorter than the observed flare duration, and implies that X-ray flares can directly probe the activity of the GRB central engine.
Document ID
20160010528
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Troja, E.
(Maryland Univ. College Park, MD, United States)
Piro, L.
(Istituto di Astrofisica Spaziale e Fisica Cosmica (INAF-IASF) Rome, Italy)
Vasileiou, V.
(Maryland Univ. College Park, MD, United States)
Omodei, N.
(Kavli Inst. for Particle Astrophysics and Cosmology Stanford, CA, United States)
Burgess, J. M.
(Alabama Univ. Huntsville, AL, United States)
Cutini, S.
(European Space Agency. ESRIN Frascati, Italy)
Connaughton, V.
(Alabama Univ. Huntsville, AL, United States)
McEnery, J. E.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Date Acquired
August 23, 2016
Publication Date
April 7, 2015
Publication Information
Publication: The Astrophysical Journal
Publisher: IOP Publishing
Volume: 803
Issue: 1
e-ISSN: 2041-8213
Subject Category
Astrophysics
Report/Patent Number
GSFC-E-DAA-TN34910
Funding Number(s)
CONTRACT_GRANT: NNM11AA01A
CONTRACT_GRANT: NNM13AA03A
CONTRACT_GRANT: NNG06EO90A
Distribution Limits
Public
Copyright
Other
Keywords
gamma-ray burst: general aEuro" radiation mechanisms: non-thermal

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