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Journal ArticleDOI

Gamma-ray bursts – a puzzle being resolved ☆

01 Aug 2000-Physics Reports (North-Holland)-Vol. 333, pp 529-553
TL;DR: The recent discovery of GRB afterglow has demonstrated that we are on the right track towards the resolution of this long standing puzzle as discussed by the authors, and the current understanding implies that GRBs signal the birth of stellar mass black holes.
About: This article is published in Physics Reports.The article was published on 2000-08-01 and is currently open access. It has received 207 citations till now. The article focuses on the topics: Gamma-ray burst & Gamma-ray burst progenitors.
Citations
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Journal ArticleDOI
TL;DR: A review of the current theoretical understanding of the physical processes believed to take place in GRB's can be found in this article, where the authors focus on the afterglow itself, the jet break in the light curve, and the optical flash that accompanies the GRB.
Abstract: Gamma-ray bursts (GRB's), short and intense pulses of low-energy $\ensuremath{\gamma}$ rays, have fascinated astronomers and astrophysicists since their unexpected discovery in the late sixties. During the last decade, several space missions---BATSE (Burst and Transient Source Experiment) on the Compton Gamma-Ray Observatory, BeppoSAX and now HETE II (High-Energy Transient Explorer)---together with ground-based optical, infrared, and radio observatories have revolutionized our understanding of GRB's, showing that they are cosmological, that they are accompanied by long-lasting afterglows, and that they are associated with core-collapse supernovae. At the same time a theoretical understanding has emerged in the form of the fireball internal-external shocks model. According to this model GRB's are produced when the kinetic energy of an ultrarelativistic flow is dissipated in internal collisions. The afterglow arises when the flow is slowed down by shocks with the surrounding circumburst matter. This model has had numerous successful predictions, like the predictions of the afterglow itself, of jet breaks in the afterglow light curve, and of the optical flash that accompanies the GRB's. This review focuses on the current theoretical understanding of the physical processes believed to take place in GRB's.

1,800 citations

Journal ArticleDOI
TL;DR: In this article, a comprehensive sample of all gamma-ray burst (GRB) afterglows with known distances is presented, and their conical opening angles are derived based on observed broadband breaks in their light curves.
Abstract: We present a comprehensive sample of all gamma-ray burst (GRB) afterglows with known distances, and we derive their conical opening angles based on observed broadband breaks in their light curves. Within the framework of this conical jet model, we correct for the geometry and we find that the gamma-ray energy release is narrowly clustered around 5 × 10^(50) ergs. We draw three conclusions. First, the central engines of GRBs release energies that are comparable to ordinary supernovae. Second, the broad distribution in fluence and luminosity for GRBs is largely the result of a wide variation of opening angles. Third, only a small fraction of GRBs are visible to a given observer, and the true GRB rate is several hundred times larger than the observed rate.

1,225 citations

Journal ArticleDOI
TL;DR: A comprehensive review of major developments in our understanding of gamma-ray bursts, with particular focus on the discoveries made within the last fifteen years when their true nature was uncovered, can be found in this paper.

864 citations

Journal ArticleDOI
TL;DR: A comprehensive review of major developments in the understanding of gamma-ray bursts can be found in this article, with particular focus on the discoveries made within the last fifteen years when their true nature was uncovered.
Abstract: We provide a comprehensive review of major developments in our understanding of gamma-ray bursts, with particular focus on the discoveries made within the last fifteen years when their true nature was uncovered. We describe the observational properties of photons from the radio to multi-GeV bands, both in the prompt emission and the afterglow phases. Mechanisms for the generation of these photons in GRBs are discussed and confronted with observations to shed light on the physical properties of these explosions, their progenitor stars and the surrounding medium. After presenting observational evidence that a powerful, collimated, jet moving at close to the speed of light is produced in these explosions, we describe our current understanding regarding the generation, acceleration, and dissipation of the jet and compare these properties with jets associated with AGNs and pulsars. We discuss mounting observational evidence that long duration GRBs are produced when massive stars die, and that at least some short duration bursts are associated with old, roughly solar mass, compact stars. The question of whether a black-hole or a strongly magnetized, rapidly rotating neutron star is produced in these explosions is also discussed. We provide a brief summary of what we have learned about relativistic collisionless shocks and particle acceleration from GRB afterglow studies, and discuss the current understanding of radiation mechanism during the prompt emission phase. We discuss theoretical predictions of possible high-energy neutrino emission from GRBs and the current observational constraints. Finally, we discuss how these explosions may be used to study cosmology, e.g. star formation, metal enrichment, reionization history, as well as the formation of first stars and galaxies in the universe.

814 citations

Journal ArticleDOI
TL;DR: In this article, it was shown that if the viscosity parameter a in the NDAF has a standard value of D0.1, these models can explain short gamma-ray bursts with durations under a second, but they are unlikely to produce long GRBs with tens or hundred of seconds.
Abstract: Many models of gamma-ray bursts (GRBs) involve accretion onto a compact object, usually a black hole, at a mass accretion rate on the order of a fraction of a solar mass per second. If the accretion disk is larger than a few tens or hundreds of Schwarzschild radii, the accretion will proceed via a convection- dominated accretion —ow (CDAF) in which most of the matter escapes to in—nity rather than falling onto the black hole. Models involving the mergers of black holewhite dwarf binaries and black hole¨ helium star binaries fall in this category. These models are unlikely to produce GRBs since very little mass reaches the black hole. If the accretion disk is smaller, then accretion will proceed via neutrino cooling in a neutrino-dominated accretion disk (NDAF) and most of the mass will reach the center. Models involving the mergers of double neutron star binaries and black holeneutron star binaries fall in this category and are capable of producing bright GRBs. If the viscosity parameter a in the NDAF has a standard value of D0.1, these mergers can explain short GRBs with durations under a second, but they are unlikely to produce long GRBs with durations of tens or hundred of seconds. If the accretion disk is fed by fallback of material after a supernova explosion, as in the collapsar model, then the time- scale of the burst is determined by fallback, not accretion. Such a model can produce long GRBs. Fall- back models again require that the accretion should proceed via an NDAF rather than a CDAF in order for a signi—cant amount of mass to reach the black hole. This condition imposes an upper limit on the radius of injection of the gas. Subject headings: accretion, accretion disksgamma rays: burstsgamma rays: theory

383 citations

References
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Journal ArticleDOI
TL;DR: In this paper, a cosmological model for gamma-ray bursts is explored in which the radiation is produced as a broadly beamed pair fireball along the rotation axis of an accreting black hole.
Abstract: A cosmological model for gamma-ray bursts is explored in which the radiation is produced as a broadly beamed pair fireball along the rotation axis of an accreting black hole. The black hole may be a consequence of neutron star merger or neutron star-black hole merger, but for long complex bursts, it is more likely to come from the collapse of a single Wolf-Rayet star endowed with rotation ('failed' Type Ib supernova). The disk is geometrically thick and typically has a mass inside 100 km of several tenths of a solar mass. In the failed supernova case, the disk is fed for a longer period of time by the collapsing star. At its inner edge the disk is thick to its own neutrino emission and evolves on a viscous time scale of several seconds. In a region roughly 30 km across, interior to the accretion disk and along its axis of rotation, a pair fireball is generated by neutrino annihilation and electron-neutrino scattering which deposit approximately 10 exp 50 ergs/s.

2,399 citations

Journal ArticleDOI
TL;DR: In this paper, the broadband spectrum and corresponding light curve of synchrotron radiation from a power-law distribution of electrons in an expanding relativistic shock were calculated for the gamma-ray burst afterglow.
Abstract: The recently discovered gamma-ray burst afterglow is believed to be described reasonably well by synchrotron emission from a decelerating relativistic shell that collides with an external medium. To compare theoretical models with afterglow observations, we calculate here the broadband spectrum and corresponding light curve of synchrotron radiation from a power-law distribution of electrons in an expanding relativistic shock. Both the spectrum and the light curve consist of several power-law segments with related indices. The light curve is constructed under two limiting models for the hydrodynamic evolution of the shock: fully adiabatic and fully radiative. We give explicit relations between the spectral index and the temporal power-law index. Future observations should be able to distinguish between the possible behaviors and determine the type of solution.

2,295 citations

Journal ArticleDOI
TL;DR: In this paper, the authors studied the time-averaged gamma-ray burst spectra accumulated by the spectroscopy detectors of the Burst and Transient Source Experiment (BTSE).
Abstract: We studied the time-averaged gamma-ray burst spectra accumulated by the spectroscopy detectors of the Burst and Transient Source Experiment. The spectra are described well at low energy by a power-law continuum with an exponential cutoff and by a steeper power law at high energy. However, the spectral parameters vary from burst to burst with no universal values. The break in the spectrum ranges from below 100 keV to more than 1 MeV, but peaks below 200 keV with only a small fraction of the spectra breaking above 400 keV; it is therefore unlikely that a majority of the burst spectra are shaped directly by pair processes, unless bursts originate from a broad redshift range. The correlations among burst parameters do not fulfill the predictions of the cosmological models of burst origin. No correlations with burst morphology or the spatial distribution were found. We demonstrate the importance of using a complete spectral description even if a partial description (e.g., a model without a high-energy tail) is statistically satisfactory.

2,288 citations

Journal ArticleDOI
13 Jul 1989-Nature
TL;DR: In this paper, it was pointed out that neutron-star collisions should synthesize neutron-rich heavy elements, thought to be formed by rapid neutron capture (the r-process), and these collisions should produce neutrino bursts and resultant bursts of gamma rays; the latter should comprise a subclass of observable gamma-ray bursts.
Abstract: It is pointed out here that neutron-star collisions should synthesize neutron-rich heavy elements, thought to be formed by rapid neutron capture (the r-process). Furthermore, these collisions should produce neutrino bursts and resultant bursts of gamma rays; the latter should comprise a subclass of observable gamma-ray bursts. It is argued that observed r-process abundances and gamma-ray burst rates predict rates for these collisions that are both significant and consistent with other estimates.

1,986 citations

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