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  • 1
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    Constraints on electron acceleration in the Crab nebula (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Using the radio through hard X-ray images of the Crab nebula to derive the spatial dependence of the electron spectrum and the magnetic field distribution from MHD flow models, we have rederived the high-energy spectrum of inverse Compton scattered gamma rays. We find agreement with the observed spectrum at TeV energies, but it is clear that the inverse Compton flux does not contribute significantly to the unpulsed nebular emission observed by COS-B from 50 to 500 MeV, which is consistent with a smooth continuation of the spectrum in hard X-rays. The emission at these energies must therefore be due to synchrotron radiation by electrons of at least PeV energies. It appears that the emission in the high-energy gamma-ray range, sensitive to the highest energy electrons in the nebula, can put interesting constraints on the acceleration mechanism.
    Keywords: SPACE RADIATION
    Type: In: Particle acceleration in cosmic plasmas; Proceedings of the Workshop, Bartol Research Inst., Newark, DE, Dec. 4-6, 1991 (A93-39976 16-93); p. 471-476.
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  • 2
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    Implications of the IRAS survey for Galactic gamma-ray astronomy (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Using the results of the IRAS far-infrared survey of the Galaxy, we have obtained the large-scale radial distributions of Galactic far infrared emission independently for both the Northern and Southern Hemisphere sides of the Galaxy. We find the dominant feature in these distributions to be a broad peak coincident with the '5 kpc' molecular gas cloud ring. We also find evidence of spiral arm features. Strong correlations are evident between the large scale Galactic distributions of far infrared emission, gamma-ray emission and CO emission. We find a particularly tight correlation between the distribution of warm molecular clouds and far-infrared emission on a Galactic scale.
    Keywords: SPACE RADIATION
    Type: In: High energy gamma-ray astronomy; Proceedings of the International Conference, Ann Arbor, MI, Oct. 2-5, 1990 (A93-25001 08-93); p. 20-24.
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  • 3
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    Resonant Compton cooling and annihilation line production in gamma-ray bursts (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Attention is given to a synchrotron self-Compton emission model for gamma-ray bursts which produces narrow annihilation features for a variety of field strengths, primary electron injection energies, and injection rates. In this model, primary electrons are injected and cooled by synchrotron emission in a strong, homogeneous magnetic field, resulting in a pair cascade. Multiple resonant scattering with cyclotron photons efficiently traps and cools pairs in the ground state to an average energy where the Compton energy loss rate is zero, which is in agreement with previous estimates of a Compton temperature. The particle distributions in the ground state are determined by numerically solving the Fokker-Planck equation in the steady state. In the case of isotropic injection of primary electrons, a significant narrow-line feature appears in the overall emission. In the case of beamed injection, the annihilation line is broadened to the extent that it would not be observable.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 386; 308-324
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  • 4
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    The galactic gamma-ray distribution - Implications for galactic structure and the radial cosmic-ray gradient (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The radial distribution of gamma ray emissivity in the Galaxy was derived from flux longitude profiles, using both the final SAS-2 results and the recently corrected COS-B results and analyzing the northern and southern galactic regions separately. The recent CO surveys of the Southern Hemisphere were used in conjunction with the Northern Hemisphere data, to derive the radial distribution of cosmic rays on both sides of the galactic plane. In addition to the 5 kpc ring, there is evidence from the radial asymmetry for spiral features which are consistent with those derived from the distribution of bright H II regions. Positive evidence was also found for a strong increase in the cosmic ray flux in the inner Galaxy, particularly in the 5 kpc region in both halves of the plane.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 291; 471-478
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  • 5
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    Cascade model of gamma-ray bursts: Power-law and annihilation-line components (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: If, in a neutron star magnetosphere, an electron is accelerated to an energy of 10 to the 11th or 12th power eV by an electric field parallel to the magnetic field, motion of the electron along the curved field line leads to a cascade of gamma rays and electron-positron pairs. This process is believed to occur in radio pulsars and gamma ray burst sources. Results are presented from numerical simulations of the radiation and photon annihilation pair production processes, using a computer code previously developed for the study of radio pulsars. A range of values of initial energy of a primary electron was considered along with initial injection position, and magnetic dipole moment of the neutron star. The resulting spectra was found to exhibit complex forms that are typically power law over a substantial range of photon energy, and typically include a dip in the spectrum near the electron gyro-frequency at the injection point. The results of a number of models are compared with data for the 5 Mar., 1979 gamma ray burst. A good fit was found to the gamma ray part of the spectrum, including the equivalent width of the annihilation line.
    Keywords: SPACE RADIATION
    Type: NASA-TM-101176 , NAS 1.15:101176 , CSSA-ASTRO-88-13
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  • 6
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    Pulsar and diffuse contributions to the observed galactic gamma radiation (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: With the acquisition of satellite data on the energy spectrum of galactic gamma-radiation, it is clear that such radiation has a multicomponent nature. A calculation of the pulsar gamma ray emission spectrum is used together with a statistical analysis of recent data on 328 known pulsars to make a new determination of the pulsar contribution to galactic gamma ray emission. The contributions from diffuse interstellar cosmic ray induced production mechanisms to the total emission are then reexamined. It is concluded that pulsars may account for a significant fraction of galactic gamma ray emission.
    Keywords: SPACE RADIATION
    Type: NASA-TM-82028
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  • 7
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    Galactic X-ray emission from pulsars (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The contribution of pulsars to the gamma-ray flux from the galactic plane is examined using data from the most recent pulsar surveys. It is assumed that pulsar gamma-rays are produced by curvature radiation from relativistic particles above the polar cap and attenuated by pair production in the strong magnetic and electric fields. Assuming that all pulsars produce gamma-rays in this way, their luminosities can be predicted as a function of period and magnetic field strength. Using the distribution of pulsars in the galaxy as determined from data on 328 pulsars detected in three surveys, the local gamma-ray production spectrum, the longitude profile, and the latitude profile of pulsar gamma-ray flux are calculated. The largest sources of uncertainty in the size of the pulsar contribution are the value of the mean interstellar electron density, the turnover in the pulsar radio luminosity function, and the average pulsar magnetic field strength. A present estimate is that pulsars contribute from 15 to 20 % of the total flux of gamma-rays from the galactic plane.
    Keywords: SPACE RADIATION
    Type: NASA-TM-82081
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  • 8
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    The galactic gamma-ray distribution and the radial cosmic ray gradient (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The radial distribution is derived of gamma ray emissivity and the cosmic ray intensity in the Galaxy using the final SAS-2 results, the recently corrected COS-B results, and recent CO surveys of the Northern and Southern Galactic Hemispheres. In addition to the 5 kpc ring of enhanced emission, there is evidence for spiral features. A strong increase in the cosmic ray flux is found in the inner Galaxy, particularly in the 5 kpc region, in both halves of the plane.
    Keywords: SPACE RADIATION
    Type: OG-3.1-4 , 19th Intern. Cosmic Ray Conf - Vol. 1; p 321-324; NASA-CP-2376-VOL-1
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  • 9
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    The galactic gamma-ray distribution: Implications for galactic structure and the radial cosmic ray gradient (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The radial distribution of gamma ray emissivity in the Galaxy was derived from flux longitude profiles, using both the final SAS-2 results and the recently corrected COS-B results and analyzing the northern and southern galactic regions separately. The recent CO surveys of the Southern Hemisphere, were used in conjunction with the Northern Hemisphere data, to derive the radial distribution of cosmic rays on both sides of the galactic plane. In addition to the 5 kpc ring, there is evidence from the radial asymmetry for spiral features which are consistent with those derived from the distribution of bright HII regions. Positive evidence was also found for a strong increase in the cosmic ray flux in the inner Galaxy, particularly in the 5 kpc region in both halves of the plane.
    Keywords: SPACE RADIATION
    Type: NASA-TM-86173 , NAS 1.15:86173
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  • 10
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    The inverse Compton gamma-ray spectrum of the Crab nebula (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The observed TeV flux from the Crab can be explained by inverse Compton scattering in the nebula if the average nebular field is indeed approximately equal to 0.0003 G as is predicted by the spectral break between radio and optical. The estimated spectral index at TeV energies also agrees with the observed value. The unpulsed high energy gamma-rays seen by COS-B are not explained by this inverse Compton component but can be explained by synchrotron radiation requiring electrons up to at least 10 exp 16 eV, most likely accelerated at the shock in the pulsar wind. The detection of a spectral depression at about 1 GeV would allow an estimate of the maximum electron energy. The flux estimates also predict the detection of a steady flux of unpulsed UHE gamma-rays from near the shock with sensitive detectors if the field strength increases downstream with increasing radius as is predicted by MHD theory.
    Keywords: SPACE RADIATION
    Type: International Cosmic Ray Conference; Aug 11, 1991 - Aug 23, 1991; Dublin
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