Jet models of X-Ray Flashes

Lamb, D. Q. and Donaghy, T. Q. and Graziani, C. (2005) Jet models of X-Ray Flashes. Il nuovo cimento C, 28 (3). pp. 365-372. ISSN 1826-9885

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Onethird of all HETE-2–localized bursts areX-Ra y Flashes (XRFs), a class of events first identified by Heise in which the fluence in the 2–30 keV energy band exceeds that in the 30–400 keV energy band. We summarize recent HETE-2 and other results on the properties of XRFs. These results show that the properties of XRFs, X-ray–rich gamma-ray bursts (GRBs), and GRBs form a continuum, and thus provide evidence that all three kinds of bursts are closely related phenomena. As the most extreme burst population, XRFs provide severe constraints on burst models and uniqueinsigh ts into thestructureof GRB jets, theGRB rate, and the nature of Type Ib/Ic supernovae. We briefly mention a number of the physical models that have been proposed to explain XRFs. We then consider two fundamentally different classes of phenomenological jet models: universal jet models, in which it is posited that all GRBs jets are identical and that differences in the observed properties of the bursts are due entirely to differences in the viewing angle; and variable-opening angle jet models, in which it is posited that GRB jets have a distribution of jet opening angles and that differences in the observed properties of the bursts are due to differences in the emissivity and spectra of jets having different opening angles. We consider three shapes for the emissivity as a function of thevie wing angle θv from theaxis of theje t: power law, top hat (or uniform), and Gaussian (or Fisher). We then discuss the effect of relativistic beaming on each of these models. We show that observations can distinguish between these various models.

Item Type: Article
Additional Information: Paper presented at the “4th Workshop on Gamma-Ray Burst in the Afterglow Era”, Rome, October 18-22, 2004.
Uncontrolled Keywords: γ-ray sources; γ-ray bursts
Subjects: 500 Scienze naturali e Matematica > 520 Astronomia e scienze connesse
Depositing User: Marina Spanti
Date Deposited: 16 Mar 2020 10:21
Last Modified: 16 Mar 2020 10:21

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