ASTROPHYSICS: A Windy Gamma-Ray Burst

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Science  19 Jan 2001:
Vol. 291, Issue 5503, pp. 399d
DOI: 10.1126/science.DOISUFFIX

The origin of gamma-ray bursts (GRB)—energetic, short-duration flashes of bright gamma rays—is unknown. Recent observations of iron-intensified x-ray emissions in the afterglow of GRB991216 about one and one-half days after the main burst (see Piro et al., Reports, 3 November 2000) have underscored the need for explanatory models. An existing two-stage model posits a supernova explosion followed several days later by the burst of gamma rays; this allows the stellar remnant to expand before the burst-induced blast wave interacts with the envelope and results in the iron-intensified emissions.

Rees and Mészáros offer an alternative scenario, beginning with a stellar collapse of either a rapidly spinning neutron star (collapsar model) or the highly magnetized torus of a black hole (magnetar model) into the GRB progenitor. The burst would occur soon afterwards, producing the bright flash followed by the decay of the x-ray continuum in the afterglow from the GRB blast wave. The iron-intensified x-ray emissions would develop later, due to the interaction of the GRB blast wave with the magnetohydrodynamic wind emanating from the recently collapsed and possibly not quite stable neutron star or black hole. — LR

Acknowledgments

Astrophys. J. 545, L73 (2000).

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