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  • SPACE RADIATION  (5)
  • ASTROPHYSICS  (4)
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  • 1
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    Compton scattering in jets: A mechanism for approximately 0.4 and less than or approximately 0.2 MeV line production (1994)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: We show that gamma-ray line emission at approximately 0.4 and less than or approximately 0.2 MeV can be produced by Compton scattering of beamed radiation in the jets of Galactic black hole candidates. This mechanism has the novel feature of not invoking the presence of e(exp +)-e(exp -) pairs. To produce the two lines, we employ a symmetric double-sided jet with bulk flow velocity of about 0.5c and incident beam radiation with a hard energy spectrum. We show that the two lines can be seen at viewing-angle cosines relative to the jet ranging from 0.2 to 0.6. This comprises 40% of the total solid angle. In addition, the line radiation is approximately 10% polarized. Depending on the bulk flow and viewing angle, the model can produce lines at other energies as well. In particular, a broad feature near 1 MeV can be seen by viewing the jet close to its axis. Our model can also accommodate single-line spectra if the beamed gamma-ray emission or the jets themselves are asymmetric.
    Keywords: SPACE RADIATION
    Type: The Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 431; 1; p. L39-L42
    Format: text
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  • 2
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    Secondary antiproton production in relativistic plasmas (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Angular and energy spectra of bremsstrahlung have been calculated from anisotropic electron distributions in solar flares. Results have been compared to observations of gamma-ray limb-brightening and the data on the variation of the gamma-ray spectrum with flare position on the sun.
    Keywords: SPACE RADIATION
    Type: Nature (ISSN 0028-0836); 319; 205
    Format: text
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  • 3
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    Secondary production of neutral pi-mesons and the diffuse galactic gamma radiation (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Isobaric and scaling model predictions of the secondary spectra of neutral pi-mesons produced in proton-proton collisions, at energies between threshold and a few GeV, are compared on the basis of accelerator data and found to show the isobaric model to be superior. This model is accordingly used, in conjuction with a scaling model representation at high energies, in a recalculation of the pi exp (0) gamma-radiation's contribution to the diffuse galactic gamma background; the cosmic ray-induced production of photons (whose energy exceeds 100 MeV) by such radiation occurs at a rate of 1.53 x 10 to the -25 photons/(s-H atom). These results are compared with previous calculations of this process as well as with COS-B observations of the diffuse galactic gamma-radiation.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 157; 2, Ma
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  • 4
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    Time-dependent behavior of active galactic nuclei with pair production (1994)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: We study the properties of coupled partial differential equations describing the time-dependent behavior of the photon and electron occupation numbers for conditions likely to be found near active galactic nuclei (AGN). The processes governing electron acceleration are modeled by a stochastic accelerator, and we include acceleration by Alfvenic and whistler turbulence. The acceleration of electrons is limited by Compton and synchrotron losses, and the number density of electrons depends on pair production and annihilation processes. We also treat particle escape from the system. We examine the steady, (possibly) oscillatory, and unstable solutions that arise for various choices of parameters. We examine instabilities related to pair production and trapping and consider the formation of pair jets.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Workshop on Physics of Accretion Disks Around Compact and Young Stars; p 2
    Format: application/pdf
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  • 5
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    Neutron and antineutron production in accretion onto compact objects (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Nuclear reactions in the hot accretion plasma surrounding a collapsed star are a source of neutrons, primarily through spallation and pion-producing reactions, and antineutrons, principally through the reaction p+p yields p+p+n+anti-n. We calculate spectra of neutrons and antineutrons produced by a variety of nonthermal energetic particle distributions in which the target particles are either at rest or in motion. If only neutral particles are free to escape the interaction site, a component of the proton and antiproton fluxes in the cosmic radiation results from the neutrons and antineutrons which leave the accretion plasma and subsequently decay in the interstellar medium. This additional antiproton component could account for the enhanced flux of antiprotons in the cosmic radiation, compared to values expected from the standard leaky-box model of cosmic-ray propagation and confinement. Moreover, the low-energy antiproton flux measured by Buffington et al. (1981) could result from target-particle motion in the accretion plasma. This model for the origin of antiprotons predicts a narrow 2.223 MeV line which could be observable.
    Keywords: SPACE RADIATION
    Type: NASA-TM-89264 , NAS 1.15:89264
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  • 6
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    Secondary antiproton production in relativistic plasmas (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The possibility is investigated that the reported excess low energy antiproton component of the cosmic radiation results from proton-proton (p-p) interactions in relativistic plasmas. Because of both target and projectile motion in such plasmas, the antiproton production threshold in the frame of the plasma is much lower than the threshold of antiproton production in cosmic ray interactions with ambient matter. The spectrum of the resultant antiprotons therefore extends to much lower energy than in the cosmic ray case. The antiproton spectrum is calculated for relativistic thermal plasmas and the spectrum is estimated for relativistic nonthermal plasmas. As possible production sites, matter accreting onto compact objects located in the galaxy is considered. Possible overproduction of gamma rays from associated neutral pion production can be avoided if the site is optically thick to the photons but not to the antiprotons. A possible scenario involves a sufficiently large photon density that the neutral pion gamma rays are absorbed by photon-photon pair production. Escape of the antiprotons to the interstellar medium can be mediated by antineutron production.
    Keywords: SPACE RADIATION
    Type: OG-6.1-4 , 19th Intern. Cosmic Ray Conf - Vol. 2; p 338-341; NASA-CP-2376-VOL-2
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  • 7
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    The production spectrum of a relativistic Maxwell-Boltzmann gas (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A formula is derived for use in the calculation of the spectrum of particles or photons produced through particle collisions in a Maxwell-Boltzmann gas. The result is valid for all temperatures and for the general case when the gas contains different mass particles. It is written in terms of a double integral over the cross section differential in the energy of the produced particles (or photons) in the center-of-momentum system of two colliding particles. Analytic expressions for the reaction rate and luminosity are also derived and reproduce the findings of previous work. Application to the problem of the annihilation spectrum from a relativistic Maxwell-Boltzmann electron-positron gas is made. Agreement is found between the present work and previous numerical and analytical studies.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 280; 328-333
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  • 8
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    High-energy gamma radiation from extragalactic radio sources (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We propose that the important relationship between 3C 273 and 3C 279, the first two extragalactic sources detected at over 100 MeV energies, is their superluminal nature. In support of this conjecture, we propose a kinematic focusing mechanism, based on Compton scattering of accretion-disk photons by relativistic nonthermal electrons in the jet, that preferentially emits gamma rays in the superluminal direction.
    Keywords: SPACE RADIATION
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 256; 2; p. L27-L30.
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  • 9
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    Binary collision rates of relativistic thermal plasmas. II - Spectra (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Spectra of importance for the analysis of relativistic thermal plasmas are numerically calculated assuming a thermal form for the particle distribution functions. Complete sets of optically thin thermal electron-proton, electron-electron, and electron-positron bremsstrahlung spectra are calculated throughout the transrelativistic regime of electron temperatures and compared with approximate expressions for the spectra in the nonrelativistic and extreme relativistic regimes of temperature. A method for calculating accurate secondary particle production spectra in proton-proton collisions from threshold to the highest energies is presented based on an isobaric model near threshold and scaling representations at high energies. The production spectra of charged and neutral pions resulting from proton-proton collisions in relativistic proton plasmas are calculated, and the resultant electron, positron, and gamma-ray spectra from the decay of secondary pions are presented.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 307; 47-59
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