138 research outputs found
Gamma Ray Burst origin and their afterglow: story of a discovery and more
In this paper we review the story of the BeppoSAX discovery of the Gamma Ray
Burst afterglow and their cosmological distance, starting from their first
detection with Vela satellites and from the efforts done before BeppoSAX. We
also discuss the consequences of the BeppoSAX discovery, the issues left open
by BeppoSAX, the progress done up to now and its perspectives.Comment: 31 pages, 14 figures, published in 2011 in the international refereed
journal "La Rivista del Nuovo Cimento" of the Italian Physical Society, vol.
34. The occasion of this review paper was the award of the Fermi Prize 2010
to their authors "For the discovery of the X-ray afterglow of Gamma-Ray Burst
with the BeppoSAX satellite"
(http://www.sif.it/SIF/en/portal/activities/fermi_award
Laue gamma-ray lenses for space astrophysics:status and prospects
We review feasibility studies, technological developments and astrophysical
prospects for Laue lenses devoted to hard X-/gamma-ray astronomy observations.Comment: 26 pages, 24 figures. Published in a special issue (Volume 2010
(2010), Article ID 215375, doi:10.1155/2010/215375) of the on-line journal
"X-Ray Optics and Instrumentation", devoted to "X-Ray Focusing: Techniques
and Applications
X-ray Emission from Gamma-Ray Bursts
SummaryIn this paper I will present and discuss some of the relevant results obtained with the Italian satellite BeppoSAX on the prompt and afterglow emission of Gamma Ray Bursts (GRBs)
X-Ray Observations of Gamma-Ray Burst Afterglows
The discovery by the BeppoSAX satellite of X-ray afterglow emission from the
gamma-ray burst which occurred on 28 February 1997 produced a revolution in our
knowledge of the gamma-ray burst phenomenon. Along with the discovery of X-ray
afterglows, the optical afterglows of gamma-ray bursts were discovered and the
distance issue was settled, at least for long -ray bursts. The 30 year
mystery of the gamma-ray burst phenomenon is now on the way to solution. Here I
rewiew the observational status of the X-ray afterglow emission, its mean
properties (detection rate, continuum spectra, line features, and light
curves), and the X-ray constraints on theoretical models of gamma-ray bursters
and their progenitors. I also discuss the early onset afterglow emission, the
remaining questions, and the role of future X-ray afterglow observations.Comment: 28 pages, 4 figures, 3 Table
An upscattering spectral formation model for the prompt emission of Gamma-Ray Bursts
We propose a model for the spectral formation of Gamma Ray Burst (GRB) prompt
emission, where the phenomenological Band's function is usually applied to
describe the GRB prompt emission. We suggest that the GRB prompt emission is
mainly a result of two upscattering processes. The first process is the
Comptonization of relatively cold soft photons of the star off electrons of a
hot shell of plasma of temperature T_e of the order of 10^{9} K (or kT_e~100
keV) that moves sub-relativistically with the bulk velocity V_b substantially
less than the speed of light c. In this phase, the Comptonization parameter Y
is high and the interaction between a blackbody-like soft seed photon
population and hot electrons leads to formation of a saturated Comptonization
spectrum modified by the sub-relativistic bulk outflow. The second process is
an upscattering of the previously Comptonized spectrum by the plasma outflow
once it becomes relativistic. This process gives rise to the high-energy
power-law component above the peak in the EF(E)-diagram where F(E) is the
energy flux. The latter process can be described by a convolution of the
Comptonized spectrum with a broken-power-law Green function. Possible physical
scenarios for this second upscattering process are discussed. In the framework
of our model, we give an interpretation of the Amati relation between the
intrinsic spectral peak photon energy and radiated energy or luminosity, and we
propose a possible explanation of the GRB temporal variability.Comment: 27 pages, 8 figures, accepted for publication in the Astrophysical
Journa
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