1,323 research outputs found
A Short History of the First 50 Years: From the GRB Prompt Emission and Afterglow Discoveries to the Multimessenger Era
No full textMore than fifty years have elapsed from the first discovery of gamma-ray bursts (GRBs) with American Vela satellites, and more than twenty-five years from the discovery with the BeppoSAX satellite of the first X-ray afterglow of a GRB. Thanks to the afterglow discovery and to the possibility given to the optical and radio astronomers to discover the GRB optical counterparts, the long-time mystery about the origin of these events has been solved. Now we know that GRBs are huge explosions, mainly ultra relativistic jets, in galaxies at cosmological distances. Starting from the first GRB detection with the Vela satellites, I will review the story of these discoveries, those obtained with BeppoSAX, the contribution to GRBs by other satellites and ground experiments, among them being Venera, Compton Gamma Ray Observatory, HETE-2, Swift, Fermi, AGILE, MAGIC, H.E.S.S., which were, and some of them are still, very important for the study of GRB properties. Then, I will review the main results obtained thus far and the still open problems and prospects of GRB astronomy
The GRB prompt emission from X- to gamma-rays
No full textThe status of the Gamma-Ray Burst observations after the BeppoSAX switch-off and a summary of the most recent outstanding results obtained from the observational studies of the prompt 2–700 keV emission of GRBs detected with BeppoSAX is reported and their impact is discussed
Prospects for Gamma-Ray Focusing Telescopes Beyond 70/100 keV
No full textI report on the prospects for focusing telescopes in the soft gamma-ray band (>70/100 keV). These telescopes could open a new window in soft gamma-ray astronomy. Indeed the current instrumentation is background limited and many open issues could be settled with deep observations in this energy band. I also discuss some of these issues and the scientific prospects of Laue lenses for space astrophysics
BeppoSAX Observations of GRBs: 10 years after
No full textThe paper is devoted to celebrate 10 yrs from the first detection of an X-ray and optical afterglow following the prompt and accurate localization of a GRB with BeppoSAX (GRB 970228). I will concentrate on some major results obtained with BeppoSAX on the GRB prompt emission. I also discuss some preliminary results of the analysis now in progress on the spectral evolution of the GRBs detected with both the GRBM and WFCs instruments aboard
X--ray observations of Gamma Ray Burst Afterglows
No full textThe discovery by the BeppoSAX satellite of X-ray afterglow emission
from the gamma-ray burst (GRB) 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 GRBs were
discovered and the distance issue was settled, at least for long GRBs.
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
GRBs and their progenitors. I also discuss the early
onset afterglow emission, the remaining questions, and the role of
future X-ray afterglow observations
Gamma-Ray Bursts origin and their afterglow: Story of a discovery and more
No full textIn this paper we review the story of the BeppoSAX discovery of the Gamma-Ray Bursts 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. © Società Italiana di Fisica
Laue Gamma-Ray Lenses for Space Astrophysics: Status and Prospects
No full textWe review feasibility studies, technological developments, and the astrophysical prospects for Laue lenses devoted
to hard X-/gamma-ray astronomy observations.</jats:p
Extremely energetic
No full textThe origin, reliability, and dispersion of the Ep,i – Eiso and other spectral energy correlations is a highly debated topic in GRB astrophysics. GRB 080916C, with its enormous radiated energy ( ~ 1055 erg in the 1 keV-10 GeV cosmological rest-frame energy band) and its intense GeV emission measured by Fermi, provides a unique opportunity to investigate this issue. In our analysis, we also study another extremely energetic event, GRB 090323, more recently detected and localized by Fermi/LAT, whose radiated energy is comparable to that of GRB 080916C
in the 1 keV-10 MeV energy range. Based on Konus/WIND and Fermi spectral measurements,
we find that both events are fully consistent with the Ep,i – Eiso correlation (updated to include 95 GRBs with the data available as of April 2009), thus further confirming and extending it,
and providing evidence against a possible flattening or increased dispersion at very high energies.
This also suggests that the physics behind the emission of peculiarly bright and hard GRBs is the same as for medium-bright and soft-weak long events (XRFs), which all follow the correlation.
In addition, we find that the normalization of the correlation obtained by considering these two GRBs and the other long ones for which was measured to high accuracy by the Fermi/GBM are fully consistent with those obtained by other instruments (e.g., BeppoSAX, Swift, Konus/WIND), thus indicating that the correlation is not affected significantly by “data truncation” because of detector thresholds and limited energy bands. A Fermi/GBM accurate estimate of the peak energy of a
very bright and hard short GRB with a measured redshift, GRB 090510, provides robust evidence that short GRBs do not follow the Ep,i – Eiso correlation and that the Ep,i – Eiso plane can be used to discriminate between, and understand, the two classes of events. Prompted by the extension of the spectrum of GRB 080916C to several GeV (in the cosmological rest-frame) without any excess or cut-off, we also investigated whether the evaluation of in the commonly adopted 1 keV-10 MeV energy band may bias the Ep,i – Eiso correlation and/or contribute to its scatter.
By computing from 1 keV to 10 GeV, the slope of the correlation becomes slightly flatter, while its dispersion does not change significantly. Finally, we find that GRB 080916C is also consistent with most of the other spectral energy correlations derived from it, with the
possible exception of the Ep,i – Eiso – tb correlation
The two large flares from SGR1900+14 observed with the BeppoSAX Gamma-Ray Burst Monitor: new results
No full textWe present the results of a thorough timing and spectral analysis of the BeppoSAX Gamma-Ray Burst Monitor data of the two large flares from SGR1900+14: the giant one of August 27, 1998 and the intermediate one of April 18, 2001. We compare the two flares, showing interesting common spectral and temporal properties, despite their apparent different profiles and fluences. New findings concerning the presence of timing noise and the time-averaged energy spectra are discussed and interpreted in the light of the magnetar model
Broadband spectra of XTE J1650-500 with BeppoSAX
No full textWe report on preliminary results of three Target of Opportunity (TOO) observations of the X-ray transient and black hole candidate XTE J1650-500 performed on 2001 September 11-12, September 21-23, and October 3-4 respectively, with the Narrow Field Instruments (0.1-200 keV) of the BeppoSAX satellite. Inspection of the light curves in different energy bands clearly shows an extreme variability both temporal and spectral. This variability has the consequence that spectra provide acceptable fits only if integrated on a temporal scale of order 104s or even less. However, all spectra are fit by the same model with some parameters that remain unchanged during the 3 TOOs, and others that dramatically change on the above time scale. The model used is a two-phase accretion disk corona model, in which a hot corona with a hybrid electron distribution comptonizes seed photons from a disk. Reflection is important and ionization seems to be very small or even zero. During the first TOO a broad Fe Kαline is clearly seen
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