June 20, 1995
The little we do know of the physical conditions in gamma-ray bursters makes them conducive to the acceleration of high-energy cosmic rays, especially if they are at cosmological distances. We find that, with the observed statistics and fluxes of gamma-ray bursts, cosmological bursters may be an important source of cosmic rays in two regions of the observed spectrum: 1. At the very-high-energy end (E>10^{19} eV), where cosmic rays must be of extragalactic origin. 2. Around and above the spectral feature that has been described as a bump and/or a knee, which occurs around 10^{15} eV, and starts at about 10^{14} eV. The occasional bursters that occur inside the Galaxy--about once in a few hundred thousand years if burst emission is isotropic; more often, if it is beamed--could maintain the density of galactic cosmic rays at the observed level in this range. These two energy ranges might correspond to two typical energy scales expected from bursters: one pertinent to acceleration due to interaction of a magnetized-fireball front with an ambient medium; the other to acceleration in the fireball itself (e.g. shock acceleration).
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December 2, 1998
To anyone who has read a scientific journal or even a newspaper in the last six months, it might appear that cosmic gamma-ray bursts hold no more mysteries: they are cosmological, and possibly the most powerful explosions in the Universe. In fact, however, bursts remain mysterious in many ways. There is no general agreement upon the nature of the event which releases the initial energy. One burst at least appears to strain the energy budget of the merging neutron star model. ...
June 29, 2001
Cosmic gamma-ray bursts are one of the great frontiers of astrophysics today. They are a playground of relativists and observers alike. They may teach us about the death of stars and the birth of black holes, the physics in extreme conditions, and help us probe star formation in the distant and obscured universe. In this review we summarise some of the remarkable progress in this field over the past few years. While the nature of the GRB progenitors is still unsettled, it now...
September 13, 1998
Highly relativistic jets from merger and accretion induced collapse of compact stellar objects, which may produce the cosmological gamma ray bursts (GRBs), are also very efficient and powerful cosmic ray accelerators. The expected luminosity, energy spectrum and chemical composition of cosmic rays from Galactic GRBs, most of which do not point in our direction, can explain the observed properties of Galactic cosmic rays.
May 18, 1995
We discuss a scenario in which the highest energy cosmic rays (CR's) and cosmological $\gamma$-ray bursts (GRB's) have a common origin. This scenario is consistent with the observed CR flux above $10^{20}\text{eV}$, provided that each burst produces similar energies in $\gamma$-rays and in CR's above $10^{20}\text{eV}$. Protons may be accelerated by Fermi's mechanism to energies $\sim10^{20}\text{eV}$ in a dissipative, ultra-relativistic wind, with luminosity and Lorentz fact...
December 6, 1996
The cosmological gamma-ray burst (GRB) model for the production of ultra- high energy cosmic rays is described, and the current observational evidence which support it discussed. Several predictions of the model are presented, which would allow it to be tested by future high energy cosmic ray and gamma- ray experiments. If the predicted signatures of the GRB model are observed, they will not only corroborate the model, but will also provide information about the source popula...
January 9, 2004
Here we propose that the excess flux of particle events of energy near 1 EeV from the direction of the Galactic Center region is due to the production of cosmic rays by the last few Gamma Ray Bursts in our Galaxy. The basic idea is that protons get accelerated inside Gamma Ray Bursts, then get ejected as neutrons, decay and so turn back into protons, meander around the inner Galaxy for some time, and then interact again, turning back to neutrons to be observed at our distance...
December 15, 1997
Gamma-ray bursts are transient events from beyond the solar system. Besides the allure of their mysterious origin, bursts are physically fascinating because they undoubtedly require exotic physics. Optical transients coincident with burst positions show that some, and probably all, bursts originate at cosmological distances, and not from a large Galactic halo. Observations of these events' spectral and temporal behavior will guide and constrain the study of the physical proce...
June 8, 2000
It has been suggested that cosmological gamma-ray bursts (GRBs) can produce the observed flux of cosmic rays at the highest energies. However, recent studies of GRBs indicate that their redshift distribution likely follows that of the average star formation rate and that GRBs were more numerous at high redshifts. As a consequence, we show that photomeson production energy losses suffered by ultrahigh energy cosmic rays coming from GRBs would produce too sharp a spectral high ...
April 2, 1999
Major advances have been made in the field of gamma-ray bursts in the last two years. The successful discovery of X-ray, optical and radio afterglows, which were predicted by theory, has made possible the identification of host galaxies at cosmological distances. The energy release inferred in these outbursts place them among the most energetic and violent events in the Universe. Current models envisage this to be the outcome of a cataclysmic event leading to a relativistical...
December 6, 2005
Gamma-ray bursts are known to be sources of high-energy gamma rays, and are likely to be sources of high-energy cosmic rays and neutrinos. Following a short review of observations of GRBs at multi-MeV energies and above, the physics of leptonic and hadronic models of GRBs is summarized. Evidence for two components in BATSE and EGRET/TASC data suggest that GRBs are sources of high-energy cosmic rays. GLAST observations will reveal the high-energy gamma-ray power and energy rel...