1,721,243 research outputs found
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
The GRB prompt emission from X- to gamma-rays
Full text linkThe 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
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
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
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
The Hard X-Ray Tails in Neutron Star Low-Mass X-Ray Binaries: BeppoSAX Observations and Possible Theoretical Explanation of the Case of GX 17+2
No full textWe report results of a new spectral analysis of two BeppoSAX observations of the Z source GX 17+2. In one of the observations, the source exhibited a power-law-like hard (>30 keV) X-ray tail, which was described in a previous work with a hybrid Comptonization model. Recent high-energy observations with INTEGRAL of a sample of low-mass X-ray binaries including both Z and atoll classes have shown that dynamical (bulk) Comptonization of soft photons is a possible alternative mechanism for producing hard X-ray tails in such systems. We start from the INTEGRAL results and exploit the broadband capability of BeppoSAX to better investigate the physical processes at work. We use GX 17+2 as a representative case. Moreover, we suggest that weakening (or disappearance) of the hard X-ray tail can be explained by increasing radiation pressure that originates at the surface of the neutron star (NS). As a result, the high radiation pressure stops the bulk inflow, and consequently, this radiation feedback from the NS surface leads to quenching of the dynamical (bulk) Comptonization
Hard X-rays from Type II bursts of the Rapid Burster and its transition toward quiescence
No full textWe report on 4 BeppoSAX Target Of Opportunity observations of MXB 1730-335, the Rapid Burster (RB), made during the 1998 February-March outburst. In the first observation, approximately 20 days after the outburst peak, the X-ray light curve showed Type II bursts at a rate of 43 hr-1. Nine days later, during the second BeppoSAX pointing, only 5 Type II bursts were detected at the beginning of the observation. During the third pointing no X-ray bursts were detected and in the fourth and final observation the RB was not detected at all. Persistent emission from the RB was detected up to 10 keV during the first three pointings. The spectra of the persistent and bursting emissions below 10 keV were best fit with a model consisting of two blackbodies. An additional component (a power law) was needed to describe the 1-100 keV bursting spectrum when the persistent emission was subtracted. To our knowledge, this is the first detection of the RB beyond 20 keV. We discuss the evolution of the spectral parameters for the bursting and persistent emission during the outburst decay. The light curve, after the second BeppoSAX pointing, showed a steepening of the previous decay trend, and a sharper decay rate leading to quiescence was observed with BeppoSAX in the two subsequent observations. We interpret this behaviour as caused by the onset of the propeller effect. Finally, we infer a neutron star magnetic field B ~ 4 x 108 Gauss
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