2 research outputs found
The electromagnetic model of Gamma Ray Bursts
I describe electromagnetic model of gamma ray bursts and contrast its main
properties and predictions with hydrodynamic fireball model and its
magnetohydrodynamical extension. The electromagnetic model assumes that
rotational energy of a relativistic, stellar-mass central source
(black-hole--accretion disk system or fast rotating neutron star) is converted
into magnetic energy through unipolar dynamo mechanism, propagated to large
distances in a form of relativistic, subsonic, Poynting flux-dominated wind and
is dissipated directly into emitting particles through current-driven
instabilities. Thus, there is no conversion back and forth between internal and
bulk energies as in the case of fireball model. Collimating effects of magnetic
hoop stresses lead to strongly non-spherical expansion and formation of jets.
Long and short GRBs may develop in a qualitatively similar way, except that in
case of long bursts ejecta expansion has a relatively short, non-relativistic,
strongly dissipative stage inside the star. Electromagnetic and fireball models
(as well as strongly and weakly magnetized fireballs) lead to different early
afterglow dynamics, before deceleration time. Finally, I discuss the models in
view of latest observational data in the Swift era.Comment: solicited contribution to Focus Issue of New Journal of Physics, 27
pages, 4 figure
GRB Fireball Physics: Prompt and Early Emission
We review the fireball shock model of gamma-ray burst prompt and early
afterglow emission in light of rapid follow-up measurements made and enabled by
the multi-wavelength Swift satellite. These observations are leading to a
reappraisal and expansion of the previous standard view of the GRB and its
fireball. New information on the behavior of the burst and afterglow on minutes
to hour timescales has led, among other results, to the discovery and follow-up
of short GRB afterglows, the opening up of the z>6 redshift range, and the
first prompt multi-wavelength observations of a long GRB-supernova. We discuss
the salient observational results and some associated theoretical issues.Comment: 23 pages. Published in the New Journal of Physics Focus Issue, "Focus
on Gamma-Ray Bursts in the Swift Era" (Eds. D. H. Hartmann, C. D. Dermer & J.
Greiner). V2: Minor change