Theory Of Gamma-ray Bursts Research Articles

The Theory of Gamma-Ray Bursts

This chapter gives a brief review on the theory of gamma-ray bursts (GRBs), including the models of multi-messengers (e.g., prompt multiwavelength electromagnetic emissions, high-energy neutrinos, ultra-high-energy cosmic rays, and gravitational waves) and central engines (in particular, mergers of binary neutron stars for short GRBs). For detailed reviews, please see (Piran in Phys. Rep. 314:575, 1999; Rev. Mod. Phys. 76:1143, 2004; Meszaros in Annu. Rev. Astron. Astrophys. 40:137, 2002; Rep. Prog. Phys. 69:2259, 2006; Zhang and Meszaros in Int. J. Mod. Phys. A 19:2385, 2004; Zhang in Chin. J. Astron. Astrophys. 7:1, 2007; Nakar in Phys. Rep. 442:166, 2007; Kumar and Zhang in Phys. Rep. 561:1, 2015).

Neutrino and cosmic-ray emission from multiple internal shocks in gamma-ray bursts.

Gamma-ray bursts (GRBs) are short-lived, luminous explosions at cosmological distances, thought to originate from relativistic jets launched at the deaths of massive stars. They are among the prime candidates to produce the observed cosmic rays at the highest energies. Recent neutrino data have, however, started to constrain this possibility in the simplest models with only one emission zone. In the classical theory of GRBs, it is expected that particles are accelerated at mildly relativistic shocks generated by the collisions of material ejected from a central engine. Here we consider neutrino and cosmic-ray emission from multiple emission regions since these internal collisions must occur at very different radii, from below the photosphere all the way out to the circumburst medium, as a consequence of the efficient dissipation of kinetic energy. We demonstrate that the different messengers originate from different collision radii, which means that multi-messenger observations open windows for revealing the evolving GRB outflows.

Fireball and Cannonball Models of Gamma-Ray Bursts Confront Observations

The two leading contenders for the theory of gamma-ray bursts (GRBs) and their afterglows, the Fireball and Cannonball models, are compared and their predictions are confronted, within space limitations, with key GRB observations, including recent observations with SWIFT

A theory of gamma-ray bursts

Recent observations and theoretical considerations have linked gamma-ray bursts with ultra-bright type Ibc supernovae (`hypernovae'). We here work out a specific scenario for this connection. Based on earlier work, we argue that especially the longest bursts must be powered by the Blandford–Znajek mechanism of electromagnetic extraction of spin energy from a black hole. Such a mechanism requires a high angular momentum in the progenitor object. The observed association of gamma-ray bursts with type Ibc supernovae leads us to consider massive helium stars that form black holes at the end of their lives as progenitors. In our analysis we combine the numerical work of MacFadyen & Woosley with analytic calculations in Kerr geometry, to show that about 10 53 erg each are available to drive the fast GRB ejecta and the supernova. The GRB ejecta are driven by the power output through the open field lines threading the black hole, whereas the supernova can be powered both by the shocks driven into the envelope by the jet, and by the power delivered into the disk via field lines connecting the disk with the black hole. We also present a much simplified approximate derivation of these energetics. Helium stars that leave massive black-hole remnants can only be made in fairly specific binary evolution scenarios, namely the kind that also leads to the formation of soft X-ray transients with black-hole primaries, or in very massive WNL stars. Since the binary progenitors will inevitably possess the high angular momentum we need, we propose a natural link between black-hole transients and gamma-ray bursts. Recent observations of one such transient, GRO J1655-40/Nova Scorpii 1994, explicitly support this connection: its high space velocity indicates that substantial mass was ejected in the formation of the black hole, and the overabundance of α-nuclei, especially sulphur, indicates that the explosion energy was extreme, as in SN 1998bw/GRB 980425. Furthermore, X-ray studies of this object indicate that the black hole may still be spinning quite rapidly, as expected in our model. We also show that the presence of a disk during the powering of the GRB and the explosion is required to deposit enough of the α nuclei on the companion.

Simulations of Binary Coalescence of a Neutron Star and a Black Hole

We present the results of Newtonian hydrodynamic simulations of the coalescence of a binary consisting of a black hole with a neutron star. The calculations show that for a wide range of initial conditions the core of the neutron star survives the initial mass transfer episode. We therefore identify black hole-neutron star binaries as the astrophysical production site of low mass neutron stars unstable to explosion. The relevance of the simulations to the theory of gamma-ray bursts is also discussed.

Gamma-ray burst theory: Back to the drawing board

view Abstract Citations (12) References (40) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Gamma-Ray Burst Theory: Back to the Drawing Board Harding, Alice K. Abstract Gamma-ray bursts have always been intriguing sources to study in terms of particle acceleration, but not since their discovery two decades ago has the theory of these objects been in such turmoil. Prior to the launch of Compton Gamma-Ray Observatory and observations by Burst and Transient Source Experiment (BATSE), there was strong evidence pointing to magnetized Galactic neutron stars as the sources of gamma-ray bursts. However, since BATSE the observational picture has changed dramatically, requiring much more distant and possibly cosmological sources. I review the history of gamma-ray burst theory from the era of growing consensus for nearby neutron stars to the recent explosion of halo and cosmological models and the impact of the present confusion on the particle acceleration problem. Publication: The Astrophysical Journal Supplement Series Pub Date: February 1994 DOI: 10.1086/191916 Bibcode: 1994ApJS...90..863H Keywords: Astronomical Models; Cosmology; Gamma Ray Bursts; Particle Acceleration; Halos; Neutron Stars; Spatial Distribution; Spectral Energy Distribution; Astrophysics; GAMMA RAYS: BURSTS; ACCELERATION OF PARTICLES full text sources ADS | data products SIMBAD (4)

Gamma-Ray Burst Theory: Back to the Drawing Board

AbstractGamma-ray bursts have always been intriguing sources to study in terms of particle acceleration, but not since their discovery two decades ago has the theory of these objects been in such turmoil. Prior to the launch of Compton Gamma-Ray Observatory and observations by BATSE, there was strong evidence pointing to magnetized Galactic neutron stars as the sources of gamma-ray bursts. However, since BATSE the observational picture has changed dramatically, requiring much more distant and possibly cosmological sources. I review the history of gamma-ray burst theory from the era of growing consensus for nearby neutron stars to the recent explosion of halo and cosmological models and the impact of the present confusion on the particle acceleration problem.Subject headings: acceleration of particles — gamma rays: bursts

A theory of gamma-ray bursts based on resonant Compton scattering

view Abstract Citations (12) References (61) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Theory of Gamma-Ray Bursts Based on Resonant Compton Scattering Vitello, Peter ; Dermer, Charles D. Abstract Photon spectra produced from the resonant Compton scattering of blackbody photons by a beam of energetic electrons and positrons are calculated. A range of surface temperatures near 1 keV and magnetic field strengths near 10 to the 12th G are studied for monoenergetic and power-law electron and positron source functions. Photon spectra similar to observed gamma-ray burst spectra are obtained for power-law beam injection functions with low-energy cutoffs. It is proposed that gamma-ray bursts are the resonant scattered emission of electron-positron pairs injected very close to the surface of a neutron star. Depending on the temperature and magnetic field, the mean free path for energy loss can be a fraction of the neutron star radius. The cyclotron features observed in gamma-ray burst spectra are due to complicated radiative transfer effects of photons with energies near the cyclotron fundamental and higher harmonics. Publication: The Astrophysical Journal Pub Date: June 1991 DOI: 10.1086/170152 Bibcode: 1991ApJ...374..668V Keywords: Black Body Radiation; Compton Effect; Gamma Ray Bursts; Magnetic Stars; Neutron Stars; Photons; Cyclotron Resonance; Electron Beams; Electron-Positron Pairs; Positrons; Radiative Transfer; Surface Temperature; Space Radiation; GAMMA RAYS: BURSTS; RADIATION MECHANISMS; STARS: MAGNETIC; STARS: NEUTRON full text sources ADS |

Local gamma ray events as tests of the antimatter theory of gamma ray bursts

Nearby examples of the antimatter ‘chunks’ postulated by Sofia and Van Horn to explain the cosmic gamma ray bursts may produce detectable gamma ray events when struck by solar system meteoroids. These events would have a much shorter time scale and higher energy spectrum than the bursts already observed. In order to have a reasonably high event rate, the local meteoroid population must extend to a distance from the Sun of the order of 0.1 pc, but the required distance could become much lower if the instrumental threshold is improved. We also examine the expected gamma ray flux for interaction of the antimatter bodies with the solar wind, and find it far below present instrumental capabilities.