摘要:

Gamma-ray bursts (GRBs) are still an enigma. In particular, the central engine, the total energy, and the very narrow distribution of peak energies challenge model builders. Motivated by recent theoretical developments (string theory, quantum gravity, critical collapse), which suggest that complete gravitational collapse can occur without singularities or event horizons, we explore how red-hole models (which lack singularities or event horizons) can solve these problems better than black-hole models. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361606

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

The gamma ray burst (GRB) is the electric explosion of a rest-star from a white dwarf in our Galactic arm. The GRB destroys all white dwarfs before they could be red. This is the first publication of a new model which is proven by known measured emissions of the GRBs compared with the emissions of the solar flares. The new model explains not only the gamma rays, their short pulses, the later peaks of continuous and redshifted afterglows, the emission of relativistic protons, the non-thermal radiation, the deficit of weak bursts (as usual goals of GRB models), but also a so far un-revealed deficit of strong GRBs and the missing cold (red) white dwarfs. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361607

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

A revived version of de Sitter’s 1913 “binary stars” argument against Ritz’s Galilean relativity general electrodynamic theory provides a means of explaining of the mechanism underlying theapparentvariability of variable stars, pulsars, and gamma-ray bursters. Numerical code to computec+vinduced intensity peaks andblueshift chirpsfor spectroscopic binaries provides graphical displays for comparison with observed light curves and spectra for different classes of variable stars. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361608

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Radio observations of supernovae can be interpreted as the interaction of the outer steep density profile of the supernovae with stellar winds from the progenitor stars. Modeling of the thermal supernova emission shows that the supernovae have massive star progenitors that are expected to have winds. Multiwavelength observations of the supernovae give additional constraints on the wind interaction which allow, in some cases, the determination of the parameters for the synchrotron emission. In the case of GRBs, thermal emission from a supernova was observed in one case and possibly in two others, but the nonthermal emission is generally the only diagnostic for determining the nature of the source. The distribution of the circumstellar matter is important for determining the progenitor object and there is some evidence for at least 2 types of progenitors among the observed afterglows. However, the density determination is complicated by a lack of knowledge of basic parameters for the synchrotron emission model. In addition, the possibilities of jet effects and a transition to subrelativistic expansion further complicate the situation. Multiwavelength observations extended over time are needed to limit the possibilities. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361609

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

The polarization of core-collapse supernovae shows that many if not all of these explosions must be strongly bi-polar. The most obvious way to produce this axial symmetry is by the imposition of a jet as an intrinsic part of the explosion process. These jets could arise by MHD processes in the formation of pulsars and be especially strong in the case of magnetars. The jets will blow iron-peak material out along the axes and other elements from the progenitor along the equator, a very different composition structure than pictured in simple spherical “onion skin” models. In extreme cases, these processes could lead to the production of &ggr;-ray bursts powered by strong Poynting flux. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361610

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

We discuss the properties of the very energetic Type Ic supernovae (SNe Ic) 1998bw and 1997ef and Type IIn supernova (SN IIn) 1997cy. SNe Ic 1998bw and 1997ef are characterized by their large luminosity and the very broad spectral features. Their observed properties can be explained if they are very energetic SN explosions(EK≳1×1052&hthinsp;erg),originating probably from the core collapse of the bareC+Ocores of massive stars(∼30–40&hthinsp;M⊙).At late times, the light curve suggests that the explosion may have been asymmetric; this may help us understand the claimed connection with GRB’s. SN IIn 1997cy is even more luminous than SN Ic 1998bw and the light curve declines more slowly than the56Codecay. We model such a light curve with circumstellar interaction, which requires an explosion energy of∼5×1052&hthinsp;erg.Because these kinetic energies of explosion are much larger than in normal core-collapse SNe, we call objects like these SNe “hypernovae.” ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361611

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

We suggest Nova Sco 1994 (GRO 1655-40) as a possible relic of a Gamma Ray Burster (GRB) and Type Ib supernova (SN) explosion, showing that there is evidence both that the black hole was spun up by accretion and that there was a supernova explosion. We use the disc energy delivered from the rotational energy of the black hole to power the SN, and give arguments that roughly equal energy goes into the GRB and into the accretion disc to power the supernova. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361612

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

A variety of stellar explosions powered by black hole accretion are discussed. All involve the failure of neutrino energy deposition to launch a strong supernova explosion. A key quantity which determines the type of high energy transient produced is the ratio of the engine operation time,tengine,to the time for the explosion to break out of the stellar surface,tbo.Stars with sufficient angular momentum produce collapsars—black holes accreting rapidly through a disk—in their centers. Collapsars can occur in stars with a wide range of radii depending on the amount of pre-collapse mass loss. The stellar radius and jet properties determine the degree of beaming of the explosion. In some cases the stellar envelope serves to focus the explosion to narrow beaming angles. The baryon loading of various models for classical GRBs formed in massive stars is examined and the consequences are explored. Fortengine>tbo,highly relativistic outflow is possible and classical GRBs accompanied by supernovae can be produced. In other cases hyper-energetic, asymmetric supernovae are produced. Longer GRBs(t≳100&hthinsp;s)can be produced by fallback following a weak neutrino-driven supernova explosion. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361613

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Using stellar binary population synthesis code we calculate the production rates and lifetimes of several types of possible GRB progenitors. We consider mergers of double neutron stars, black holes and neutron stars, black holes and white dwarfs, and helium stars. We calibrate the results with the measured star formation rate history. We discuss the viability of each GRB model, and alternatively, assuming that all bursts are connected with one model, we constrain the required collimation of GRBs. We also show the importance of widely used evolutionary parameters on the merger rates of calculated binary populations. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361614

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

We review the current progenitors of the rapidly accreting black holes which are thought to power gamma-ray bursts. Differences in the evolutionary scenarios of these progenitors lead to differences in the observed properties of the bursts (e.g., burst duration, burst location, and afterglow emission). We pay particular attention to the differences between helium merger and collapsar gamma-ray burst progenitors (the two leading progenitors for long-duration gamma-ray bursts). ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361615

出版商:AIP    

年代:1900

数据来源: AIP