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  • 1
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    Relativistic electron-positron beams in gamma-ray bursters (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-08-14
    Description: Beams of relativistic electrons and/or positrons leaving the surface of a strongly magnetized neutron star may give rise to gamma-ray bursts. The beams could be accelerated by strong, magnetically aligned electric fields that are produced by oscillations of the stellar surface. Here we investigate the particle acceleration in these electric fields, the resulting electron-positron pair cascade, and the gamma-ray emission. We find that beams of electrons and positrons moving parallel to the magnetic field are generated, with a reported differential energy distribution. These beams produce the bulk of the gamma-ray burst radiation below about 1 MeV by the resonant Compton scattering of thermal photons emitted from the stellar surface. The escaping synchrotron radiation from the cascade dominates the radiation spectrum above about 1 MeV.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 410; 1; p. 315-322.
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  • 2
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    Disk plus halo models of gamma-ray burst sources (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: The present consideration of Gaussian halo, exponential halo, and standard 'dark matter' halo forms for the distribution of Galactic halo sources indicates that about 70 percent of the gamma-ray bursts observed by the BATSE program can come from local Galactic disk neutron stars, with the rest lying in an extended Galactic halo. Two specific disk-halo combinations are considered as examples which use an exponential disk; in the first case, this is combined with a Gaussian halo, and in the second, with a dark matter halo.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 410; 1; p. L23-L26.
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  • 3
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    TeV gamma rays from millisecond pulsars and the detectability of globular clusters (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: I investigate the detectability of TeV gamma rays from millisecond pulsars, assuming the energy source that powers this emission is the loss of rotational energy of the spinning neutron star. I show that although individual sources may be too weak to detect, the contribution of many (about 1000) active millisecond pulsars may lead to currently detectable TeV gamma-ray emissions from globular clusters, provided the average pulsar converts about 0.1 percent of its spin-down energy into TeV gamma rays. Future detections of TeV gamma rays from globular clusters (or more restrictive upper limits on the fluxes) will lead to better estimates of the number of active millisecond pulsars the clusters contain, and to a better understanding of the pulsar emission mechanism. I also derive flux estimates for the following sources: (1) the Crab Nebula, (2) PSR 19374-21, PSR 1953 4-29, and PSR 1855 4-09, and (3) nearby millisecond pulsars in the galactic disk.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 408; 2; p. 468-470.
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  • 4
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    Multiple scattering in wind models of gamma-ray bursts (1992)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: In wind models of gamma-ray bursts, it has been assumed that soft X-ray photons are scattered only once by relativistic electrons moving away from the star; this assumes that the scattering optical depth is small. Using the observational data from the bursts, we consider three methods for estimating this optical depth: (1) the luminosity of the burst, (2) the ratio of the gamma-ray flux (greater than 10 keV) to X-ray flux (less than 10 keV), and (3) the presence or lack of cyclotron lines. Within the context of the wind models, we find that multiple scattering is likely to be important in the formation of the spectrum in gamma-ray bursts.
    Keywords: ASTROPHYSICS
    Type: In: Gamma-ray bursts; Proceedings of the Workshop, Univ. of Alabama, Huntsville, Oct. 16-18, 1991 (A93-40051 16-93); p. 241-245.
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  • 5
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    Proton acceleration in neutron star magnetospheres (1992)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: To explain the emission of TeV and PeV gamma rays from accreting X-ray binary sources, protons must be accelerated to several times the gamma-ray energy. It is shown here that at certain times, the plasma in the accretion column of the neutron star may form a deep enough pool that the top portion becomes unstable to convective motions in spite of the strong magnetic field. The resulting turbulence produces fluctuations in the strength of the magnetic field that travel up the accretion column, taking energy out to the region of the energetic protons. The protons resonantly absorb this energy and are accelerated to high energies. Including the synchrotron radiation losses of the protons, it is shown that they can be accelerated to energies that are high enough to explain the gamma-ray observations.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 388; 148-163
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  • 6
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    Particle acceleration in accreting magnetospheres (1988)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The possibility that energetic protons are accelerated within the closed magnetosphere of accelerating neutron stars is considered. The accelerating mechanism is suggested to be plasma turbulence excited by the accretion flow. Rough estimates show that this mechanism may be capable of accelerating protons to the energies of about 10 to the 16th eV required to explain observations of about 10 to the 15th eV gamma rays from some thermal X-ray sources. Proton synchrotron radiation may be observable at energies ranging from the infrared to about GeV gamma rays.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 326; 733-737
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