6533b82afe1ef96bd128c1c2
RESEARCH PRODUCT
On the existence of a reverse shock in magnetized gamma-ray burst ejecta
Petar MimicaDimitrios GianniosM. A. Aloysubject
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]description
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, there is always a relativistic or mildly relativistic reverse shock forming in σ0 <∼ 0.3 ejecta. From this, we conclude that the paucity of optical flashes, believed to be a distinctive signature of a reverse shock, may be explained by the existence of dynamically important magnetic fields in the ejecta. mimica@uv.es; aloy@uv.es
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2007-12-04 |