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On the existence of a reverse shock in magnetized gamma-ray burst ejecta

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On the existence of a reverse shock in magnetized gamma-ray burst ejecta

dc.contributor.author	Mimica, Petar
dc.contributor.author	Giannios, Dimitrios
dc.contributor.author	Aloy Toras, Miguel Angel
dc.date.accessioned	2010-08-10T10:56:31Z
dc.date.available	2010-08-10T10:56:31Z
dc.date.issued	2008
dc.identifier.uri	http://hdl.handle.net/10550/16814
dc.description.abstract	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.	en
dc.language.iso	en	en
dc.relation	http://www.aanda.org/index.php?option=com_article&access=doi&doi=10.1051/0004-6361:20078931&Itemid=129	en
dc.source	Giannios, D., Mimica, P. and Aloy, M. A. (2008): On the existence of a reverse shock in magnetized gamma-ray burst ejecta, Astronomy and Astrophysics, núm. 478, vol.3, pp. 747-753	en
dc.subject	Gamma rays : bursts; Magnetohydrodynamics (MHD); Shock waves	en
dc.title	On the existence of a reverse shock in magnetized gamma-ray burst ejecta	en
dc.type	info:eu-repo/semantics/article	en
dc.type	info:eu-repo/semantics/publishedVersion	en
dc.subject.unesco	UNESCO::ASTRONOMÍA Y ASTROFÍSICA	en
dc.subject.unesco	UNESCO::ASTRONOMÍA Y ASTROFÍSICA::Otras especialidades astronómicas	en
dc.identifier.doi	10.1051/0004-6361:20078931	en
dc.description.private	mimica@uv.es; aloy@uv.es	en
dc.identifier.idgrec	041819	en