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  • 1
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    Diffuse galactic annihilation radiation (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The study reports observations of positron annihilation radiation from the inner region of the Galaxy which show that there are two components of the radiation: a steady, diffuse Galactic component and a variable component from discrete, presumably compact sources. The existence of the variable component is supported by the ensemble of all narrow FOV 511 keV line observations, including recent detections with OSSE. The fit of this ensemble to a time-independent source distribution can be excluded at the approximately 3-sigma level. The same ensemble, combined with the broad FOV SMM observations of Galactic 511 keV line emission, sets constraints on the Galactic distribution of the diffuse component.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics Supplement Series (ISSN 0365-0138); 97; 1; p. 127-131.
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  • 2
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    Gamma-ray lines - A new window to the Universe (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Gamma-ray emission is considered in terms of its usefulness in determining the physics of nucleosynthesis, the interstellar medium, solar flares, supernovae, and neutron stars. The mechanism of gamma-ray line emission is reviewed, i.e., nuclear deexcitation, radiative capture, positron annihilation, and possibly cyclotron radiation in the strong magnetic fields of neutron stars. Various gamma-ray spectra, obtained from balloon and satellite data, are analyzed with attention to solar particle energies and densities, including particle emission from black-hole supernova remnants.
    Keywords: ASTROPHYSICS
    Type: Physics Today; 31; Mar. 197
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  • 3
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    Synchrotron cooling and annihilation of an e/+/-e/-/ plasma - The radiation mechanism for the 5 March, 1979 transient (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Positron-electron pair radiation is examined as a mechanism that could be responsible for the impulsive phase emission of the 5 March, 1979 transient. Synchrotron cooling and subsequent annihilation of the pairs can account for the energy spectrum, the very high brightness, and the 0.4 MeV feature observed from this transient, whose source is likely to be a neutron star in the supernova remnant N49 in the Large Magellanic Cloud. In this model, the observed radiation is produced in the skin layer of a hot, radiation-dominated pair atmosphere, probably confined to the vicinity of the neutron star by a strong magnetic field. In this layer, about 10 to the 12th generations of pairs are formed (by photon-photon collisions), cooled and annihilated during the 0.15 s duration of the impulsive phase.
    Keywords: ASTROPHYSICS
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  • 4
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    Origin of the 5 March 1979 gamma-ray transient - A vibrating neutron star (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: An unusual gamma-ray transient was observed on 5 March 1979, with 12 different instruments on 9 different spacecraft. The source position of the 5 March transient, determined to an accuracy of 1 x 2 arcmin, is consistent with the direction of the supernova remnant N49 in the Large Magellanic Cloud (LMC). Subsequent analysis of the data, by narrowing the source error box to an area of about 6 by 30 arcsec inside the supernova remnant, considerably strengthens this identification. It is proposed that a vibrating neutron star in the LMC is the source of the 5 March transient. This may be both the first detection of a vibrating neutron star and indirect evidence for gravitation radiation.
    Keywords: ASTROPHYSICS
    Type: Nature; 287; Sept. 11
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  • 5
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    Supernova radio remnants and the filling factor of the hot interstellar medium (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: If a hot (temperature of about one-million K), tenuous gas fills about 90% of interstellar space, then the observed number and surface brightness distribution of galactic radio remnants implies a galactic supernova rate of once about every 30 years. This is consistent with estimates based on observations of historical supernovae, pulsars, and supernovae in other spiral galaxies.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 239
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  • 6
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    A 164-day period in gamma-ray bursts from GBS0526-66? (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Evidence is presented for a pattern in the recurrence time of gamma ray bursts from GBS0526-66, showing an apparent period of 164 days. It is suggested that this pattern reflects periodic accretion to a neutron star from an eccentric binary companion. It is proposed that this system drives two types of bursts: (1) the relatively frequent but weak recurrent bursts produced by either magnetospheric gating, or thermonuclear runaway, of periodically accreting matter around the neutron star, and (2) the much rarer intense bursts produced by tidally triggered star quakes.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 312; 737-740
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  • 7
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    Gamma-ray line astronomy (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Gamma-ray astronomy is a valuable source of information on solar activity, supernovae, and nucleosynthesis. Cosmic gamma-ray lines were first observed from solar flares and more recently from the galactic center and a transient event. The latter may give an important insight into nuclear reactions taking place near neutron stars and black holes and a measure of the gravitational redshifts of such objects.
    Keywords: ASTROPHYSICS
    Type: Nature; 278; Mar. 8
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  • 8
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    Positron-electron annihilation radiation from the Galactic Center (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Evidence and arguments are presented supporting the theory that the 0.511 MeV line observed from the Galactic Center stems from photon-photon pair production near a black hole with a mass not greater than approximately 500 solar masses. Observations are reviewed and the subsequent implications on the annihilation site and the positron source are discussed. Because of the variations and line width of the e(+) - e(-) annihilation radiation from the Galactic Center, positrons must essentially be produced by a single source and annihilate in an ambient gas of density greater than 10 to the 5th/cu cm, an ionization fraction greater than 10 percent, a temperature less than 5 x 10 to the 4th K, and be confined to a region of size less than 10 to the 18th cm. Such conditions may exist in warm clouds and other IR sources within the central parsec of the Galaxy.
    Keywords: ASTROPHYSICS
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  • 9
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    The Origin of the Galactic Annihilation Radiation (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Observations of the e(+)-e(-) annihilation radiation from the galactic center are reviewed and the implications of these and other observations on the positron production process, the annihilation region and the fundamental nature of the galactic center source are discussed.
    Keywords: ASTROPHYSICS
    Type: NASA(Goddard Space Flight Center Contrib. to the Workshop on Positron-Electron Pairs in Astrophys.; p 57-62
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  • 10
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    Galactic dual population models of gamma-ray bursts (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We investigate in more detail the properties of two-population models for gamma-ray bursts in the galactic disk and halo. We calculate the gamma-ray burst statistical properties, mean value of (V/V(sub max)), mean value of cos Theta, and mean value of (sin(exp 2) b), as functions of the detection flux threshold for bursts coming from both Galactic disk and massive halo populations. We consider halo models inferred from the observational constraints on the large-scale Galactic structure and we compare the expected values of mean value of (V/V(sub max)), mean value of cos Theta, and mean value of (sin(exp 2) b), with those measured by Burst and Transient Source Experiment (BATSE) and other detectors. We find that the measured values are consistent with solely Galactic populations having a range of halo distributions, mixed with local disk distributions, which can account for as much as approximately 25% of the observed BATSE bursts. M31 does not contribute to these modeled bursts. We also demonstrate, contrary to recent arguments, that the size-frequency distributions of dual population models are quite consistent with the BATSE observations.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 434; 2; p. 552-556
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