Search results for "Gamma rays : bursts"

showing 2 items of 2 documents

Deceleration of arbitrarily magnetized GRB ejecta: the complete evolution

2008

(Abridged) We aim to quantitatively understand the dynamical effect and observational signatures of magnetization of the GRB ejecta on the onset of the afterglow. We perform ultrahigh-resolution one-dimensional relativistic MHD simulations of the interaction of a radially expanding, magnetized ejecta with the interstellar medium. The need of ultrahigh numerical resolution derives from the extreme jump conditions in the region of interaction between the ejecta and the circumburst medium. We study the evolution of an ultrarelativistic shell all the way to a the self-similar asymptotic phase. Our simulations show that the complete evolution can be characterized in terms of two parameters, name…

Magnetohydrodynamics (MHD)Astrophysics::High Energy Astrophysical PhenomenaFOS: Physical sciencesAstrophysicsAstrophysicsUNESCO::ASTRONOMÍA Y ASTROFÍSICAShock wavesMagnetizationsymbols.namesakeGamma rays : bursts; Methods : numerical; Magnetohydrodynamics (MHD); Shock wavesUNESCO::ASTRONOMÍA Y ASTROFÍSICA::Otras especialidades astronómicasEjectaAstrophysics::Galaxy AstrophysicsPhysicsnumerical [Methods]Magnetic energyAstrophysics (astro-ph)Astronomy and AstrophysicsAfterglowInterstellar mediumLorentz factorbursts [Gamma rays]Space and Planetary SciencesymbolsMagnetohydrodynamicsGamma-ray burst:ASTRONOMÍA Y ASTROFÍSICA [UNESCO]:ASTRONOMÍA Y ASTROFÍSICA::Otras especialidades astronómicas [UNESCO]
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On the existence of a reverse shock in magnetized gamma-ray burst ejecta

2007

The role of magnetic fields in gamma-ray burst (GRB) flows remains controversial. The study of the early afterglow phases and, in particular, of the reverse shock dynamics and associated emission offers a promising probe of the magnetization of the ejecta. In this paper, we derive the conditions for the existence of a reverse shock in arbitrarily magnetized ejecta that decelerate and interact with the circumburst medium. Both constant and wind-like density profiles are considered. We show, in contrast to previous estimates, that ejecta with magnetization σ0 >∼ 1 are not crossed by a reverse shock for a large fraction of the parameter space relevant to GRB flows. Allowing for shell spreading…

PhysicsMagnetohydrodynamics (MHD)Astrophysics::High Energy Astrophysical PhenomenaAstronomy and AstrophysicsAstrophysicsParameter spaceUNESCO::ASTRONOMÍA Y ASTROFÍSICAShock (mechanics)Magnetic fieldAfterglowShock wavesMagnetizationGamma rays : bursts; Magnetohydrodynamics (MHD); Shock wavesbursts [Gamma rays]Space and Planetary ScienceUNESCO::ASTRONOMÍA Y ASTROFÍSICA::Otras especialidades astronómicasEjectaGamma-ray burstAstrophysics::Galaxy Astrophysics:ASTRONOMÍA Y ASTROFÍSICA [UNESCO]:ASTRONOMÍA Y ASTROFÍSICA::Otras especialidades astronómicas [UNESCO]
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