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  • ASTROPHYSICS  (157)
  • SPACE SCIENCES
  • 1985-1989  (157)
  • 1
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    VLBI observations of the compact components in M82 (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: VLBI observations at 2.3 and 8.4 GHz of 15 compact components in M82, obtained on May 19, 1983, are examined. Angular sizes and linear sizes of the compact sources in M82 are estimated; it is detected that most of the compact sources studied have linear sizes in excess of 0.3 pc. The brightness distribution of the strongest of the 15 compact sources, 41.9 + 58, is investigated; two dominant, elongated components oriented at an angle of about 20 deg and having maximum dimensions of 10-30 mas are observed.
    Keywords: ASTROPHYSICS
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  • 2
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    VLBI limits on the proper motion of the 'core' of the superluminal quasar 3C345 (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: VLBI (very-long-baseline interferometry) observations between 1971 and 1983 have been used to determine the positions of the 'core' of the quasar 3C345 relative to the more distant compact quasar NRAO512 with a fractional uncertainty as small as two parts in a hundred million. The core of 3C345 appears stationary in right ascension to within 20 arc microsec/yr, a subluminal bound corresponding to 0.7c. The apparent velocities of the jets are superluminal, up to 14c in magnitude.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 319; 733-738
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  • 3
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    Detection of H I, OH, CO, and optical imaging of the distant galaxy IRAS 12112 + 0305 (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The detection of H I absorption and OH and CO emission from the galaxy IRAS 12112 + 0305, which is receding from the sun at about 7 percent of the speed of light is reported. This galaxy, which appears to be an ongoing merger, radiates about 2 x 10 to the 12th solar luminosities in the infrared. The H I, OH, and CO spectra are indicative of large turbulent motions. From the millimeter wave CO observations, a total mass of molecular gas of 4 x 10 to the 10th solar masses is inferred. The OH emission in the 1667 MHz line is the most luminous extragalactic OH maser reported so far, with an isotropic luminosity of 1800 solar luminosities.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 324; L59-62
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  • 4
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    Radar observations of Comet Halley (1989)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Five nights of Arecibo radar observations of Comet Halley are reported which reveal a feature in the overall average spectrum which, though weak, seems consistent with being an echo from the comet. The large radar cross section and large bandwidth of the feature suggest that the echo is predominantly from large grains which have been ejected from the nucleus. Extrapolation of the dust particle size distribution to large grain sizes gives a sufficient number of grains to account for the echo. The lack of a detectable echo from the nucleus, combined with estimates of its size and rotation rate from spacecraft encounters and other data, indicate that the nucleus has a surface of relatively high porosity.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 338; 1094-110
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  • 5
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    Supernova 1987A - A radiosphere resolved with VLBI five days after the neutrino burst (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The results of VLBI observations of SN1987A are reported. No emission from the supernova above a level of about 20 percent of the supernova's total flux density was detected, although signals were detected from two calibrator sources with amplitudes roughly equal to those determined in earlier VLBI observations. It is inferred that the supernova's radiosphere was resolved, and a lower bound on the radiosphere's radius of 2.2 mas is estimated from an epoch 5.2 days after the neutrino burst. Given the photometric data from the supernova, a distance to the LMC of 50 + or - 5 kpc, and an apparent expansion velocity that varied systematically with time from 18,000-16,000 km/s, as estimated from the blue-shifted H-alpha absorption lines on the days preceding the observations, it is concluded that 5.2 days after the neutrino burst the supernova's radiosphere was at least 2.5 times larger than the inferred blackbody photosphere, and at least as large as the H-alpha line-forming region.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 334; 412-415
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  • 6
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    Molecular gas in the powerful radio galaxies Perseus A and 4C 12.50 (1989)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Perseus A, 4C 12.50, and Cygnus A have been observed in the CO(J = 1 to 0) line. In Perseus, an estimate of 3.2 x 10 to the 9th solar masses is found for the molecular gas in the giant galaxy in the cluster center. An upper limit of M(H2) = 9 x 10 to the 9th solar masses is obtained for the galaxy in the center of Cygnus A. The results suggest that large amounts of molecular gas, and thus high rates of star formation, are involved in the genesis of the central engines that power extragalactic radio sources.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 340; L9-L12
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  • 7
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    Multifrequency observations of blazars. I - The shape of the 1 micron to 2 millimeter continuum (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Near-simultaneous measurements in 11 wavebands between 1 micron and 2 mm of a sample of 13 'blazars' are presented. These measurements represent the first comprehensive attempt to determine the infrared-to-millimeter-wave properties of this class of object, which emit the bulk of their luminosity in the far-infrared region. Most of the sources have very flat millimeter/submillimeter spectra up to the highest observed frequency. However, 3C 279 and 3C 446 show evidence of turnovers in their submillimeter spectra. The 1-4 micron spectra can be characterized by simple power laws, all steeper than -0.9; several sources, however, show evidence of spectral beaks in the 10-20 micron region, suggestive of energy losses. It is shown that the spectral properties are consistent with synchrotron emission from relativistic jets aligned close to the line of sight and the observations are discussed in relation to such models.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 291; 511-517
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  • 8
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    A processing method and results of meteor shower radar observations (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Studies of meteor showers permit the solving of some principal problems of meteor astronomy: to obtain the structure of a stream in cross section and along its orbits; to retrace the evolution of particle orbits of the stream taking into account gravitational and nongravitational forces and to discover the orbital elements of its parent body; to find out the total mass of solid particles ejected from the parent body taking into account physical and chemical evolution of meteor bodies; and to use meteor streams as natural probes for investigation of the average characteristics of the meteor complex in the solar system. A simple and effective method of determining the flux density and mass exponent parameter was worked out. This method and its results are discussed.
    Keywords: ASTROPHYSICS
    Type: International Council of Scientific Unions, Middle Atmosphere Program. Handbook for MAP, Volume 25; p 272-279
    Format: application/pdf
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  • 9
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    On the spatial structure of the Perseids meteor stream (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The analysis of radar observations of the Perseid meteor stream conducted in an ionospherical laboratory in the period from 1964 to 1981 is presented. The Perseids meteor rates were determined by the fluctuation method. Analysis of their hourly distributions showed that the stream maximum position is different for different years, i.e., the stream nodal position is constantly changing. The results of the analysis are presented and discussed.
    Keywords: ASTROPHYSICS
    Type: International Council of Scientific Unions, Middle Atmosphere Program. Handbook for MAP, Volume 25; p 339-343
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  • 10
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    A model of inner cometary ionospheres (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A hydrodynamical model to describe the movement of the thermalized charged components in the inner ionosphere of comet Halley is presented. Photoelectrons are included by applying a two-stream-type approach. The numerical scheme describes shock transitions in a natural way. Solutions are obtained for a number of different assumptions concerning electron heating rates but all show that the electron temperature increases sharply where the collisional electron neutral coupling becomes unimportant. This temperature increase is accompanied by an increase in the plasma pressure and in its associated polarization electric field, and causes the plasma flow to go subsonic. In certain cases this transition occurs as an inner shock which may explain the observed ion pile-up in Halley's comet.
    Keywords: ASTROPHYSICS
    Type: ESA Proceedings of the 20th ESLAB Symposium on the Exploration of Halley's Comet. Volume 1: Plasma and Gas; p 235-239
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