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  • 1
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    Two populations and models of gamma ray bursts (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Gamma-ray burst statistics are best explained by a source population at cosmological distances, while spectroscopy and intensity histories of some individual bursts imply an origin on Galactic neutron stars. To resolve this inconsistency I suggest the presence of two populations, one at cosmological distances and the other Galactic. I build on ideas of Shemi and Piran (1990) and of Rees and Mesozaros (1992) involving the interaction of fireball debris with surrounding clouds to explain the observed intensity histories in bursts at cosmological distances. The distances to the Galactic population are undetermined because they are too few to affect the statistics of intensity and direction; I explain them as resulting from magnetic reconnection in neutron star magnetospheres. An appendix describes the late evolution of the debris as a relativistic blast wave.
    Keywords: SPACE RADIATION
    Type: NASA-CR-194762 , NAS 1.26:194762
    Format: application/pdf
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  • 2
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    Relativistic shock spectra: A prediction (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: I argue that particles heated by relativistic shocks should assume an equilibrium energy distribution. This leads to a synchrotron spectrum F(sub nu) varies as nu(sup 1/3) up to approximately the critical frequency nu(sub 0) of an electron with the mean electron energy. Application to gamma ray bursts (GRB's) implies that a burst with 10(exp -5) erg/(sq cm s) of soft gamma-rays and h(nu(sub 0)) = 300 KeV should be about 18th magnitude in visible light and a few micro-Jy at 1 GHz (less if self-absorbed).
    Keywords: SPACE RADIATION
    Type: NASA-CR-194764 , NAS 1.26:194764
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  • 3
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    Radio and optical emission: Spectral shapes and breaks in GRB (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Relativistic blast wave models of Gamma Ray Bursts (GRB) predict the spectrum of the emitted synchrotron radiation. The electrons in the shocked region are heated to a Wien distribution whose 'temperature' is 1/3 of the mean electron energy. This energy determines a characteristic (break) frequency of synchrotron radiation. At much lower frequencies, a spectrum F(sub nu) varies as nu(sup 1/3) is predicted independently of the details of the emitting region. This is consistent with the observed soft x ray emission of GRB. It implies low visible and radio intensities, unless there are collective emission processes.
    Keywords: SPACE RADIATION
    Type: NASA-CR-194763 , NAS 1.26:194763
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  • 4
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    Implications of photometric and spectroscopic periods of SS433 (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: It is suggested that a comparison of the periodicities inferred from spectroscopic and photometric observations of SS433 may help clarify its structure. The interaction between the orbital and beam motions may produce sideband periods in the photometry. It is found that Lense-Thirring and slaved disk models make differing predictions.
    Keywords: ASTRONOMY
    Type: Astronomy and Astrophysics; 95; 2, Ma; Mar. 198
    Format: text
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  • 5
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    The bizarre spectrum of SS 433 (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Results are reported for extensive spectrophotometric observations, over the wavelength range from 3800 to 7800 A, of the peculiar 14th-mag emission-line object Stephenson-Sanduleak (SS) 433, which has been identified with a variable nonthermal radio source and is positionally coincident with the X-ray source A1909+04. It is found that the spectrum is dominated by intense variable Balmer and He I emission, that three of the He I lines have very prominent P Cygni profiles, and that virtually all the emission features undergo changes in equivalent width on a time scale of days. Anomalous emission features are described which consist of three previously unreported, very strong, broad emission lines at unfamiliar wavelengths in the green, red, and IR, and which vary nightly in intensity, profile, and wavelength. SS 433 is inferred to be a luminous object with an absolute visual magnitude of -3.1 or brighter.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 230
    Format: text
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  • 6
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    Low-frequency spectra of gamma-ray bursts (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Particles with energies below the mean energy E(sub 0) in relativistic shocked plasmas should assume an equilibrium energy distribution. This leads to a synchrotron spectrum F(sub nu) proportional to nu(exp 1/3) up to approximately the critical frequency nu(sub 0) of an electron with the energy E(sub 0). Application to gamma-ray bursts (GRBs) implies that a burst with 10(exp -5) ergs/sq cm/s of soft gamma rays and h nu(sub 0) = 300 keV should simultaneously be about 18th magnitude in visible light and a few micro-J at 1 GHz (less if self-absorbed); the low-freqency intensities peak later at higher values.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 432; 2; p. L107-L109
    Format: text
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  • 7
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    Radiation transfer in gamma-ray bursts (1992)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: We have calculated gamma-ray radiative transport in regions of high-energy density, such as gamma-ray burst source regions, using a discrete ordinate, discrete energy group method. The calculations include two-photon pair production and annihilation, as well as three-photon annihilation. The radiation fields itself acts as an absorbing medium, and the optical depth depends on its intensity, so the problem is intrinsically nonlinear. Spherical divergence produces effective collimation of the flux. At high optical depth the high energy (E is greater than 1 MeV) portion of the emergent spectrum assumes a nearly universal form. An approximate limit is derived for the high-energy flux from a gamma-ray burst source region of given size, and the implications of this limit for the distance to the 1979 March 5 event are briefly discussed. We discuss more generally the problem of very luminous bursts, and implications of Galactic halo distances for flare models.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 399; 1; p. 100-107.
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  • 8
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    Yet another model of soft gamma repeaters (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-08-27
    Description: We develop a model of soft gamma repeaters (SGRs) in which a supernova leaves planets orbiting a neutron star in intersecting orbits. These planets will collide in approximately 10(exp 4) yr if their orbits are coplanar. Some fragments of debris lose their angular momentum in the collision and fall onto the neutron star, producing a SGR. The initial accretion of matter left by the collision with essntially no angular momentum may produce a superburst like that of 1979 March 5, while debris fragments which later lose their angular momentum produce an irregular but non-Poissonian pattern of smaller bursts resembling those observed in spectrum and duration.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 437; 2; p. 727-732
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