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Swift and Fermi observations of X-ray flares: the case of Late Internal Shock
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2015 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 803, no 1Article in journal (Refereed) PublishedText
Abstract [en]

Simultaneous 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 (Γ > 50) outflow at radii R ∼ 1013-1014 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.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2015. Vol. 803, no 1
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Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:kth:diva-184447DOI: 10.1088/0004-637X/803/1/10ISI: 000353015400010ScopusID: 2-s2.0-84927591081OAI: diva2:916032

QC 20160331

Available from: 2016-03-31 Created: 2016-03-31 Last updated: 2016-03-31Bibliographically approved

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Burgess, James Michael
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