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  • ASTROPHYSICS  (198)
  • 1980-1984  (198)
  • 1970-1974
  • 1984  (198)
  • 1
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    Evolution of the ultraviolet coma of comet Austin (1982g.) (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Ultraviolet spectra of comet Austin (1982) obtained in July 1982 at heliocentric distances ranging from 1.10 to 0.81 AU preperihelion with the IUE reveal that the comet is very similar in chemical composition and appearance to comet Bradfield (1979X). In addition, the derived H2O production rate is found to vary with heliocentric distance as r to the -3.6, similar to the r to the -3.7 behavior found for comet Bradfield. It is pointed out, however, that the limited sample rate precludes the observation of the short-term variations which could be produced by a rotating nonuniform cometary nucleus.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 131; 2 Fe
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  • 2
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    Far-infrared spectroscopy of the galactic center - Neutral and ionized gas in the central 10 parsecs of the Galaxy (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The present mapping of the 3P1-3P2 fine structure line emission from neutral atomic oxygen near the galactic center shows the emission to be extended over more than 12 pc along the galactic plane, centered on the position of Sgr A West. The rotational velocity of the O I gas at R of about 1 corresponds to a mass within the central parsec of about 3 million solar masses. The forbidden O I line probably arises in a predominantly neutral atomic region immediately outside the ionized central parsec of the Galaxy. Gas temperatures are greater than 100 K, and the total integrated luminosity radiated in the line, which is about 100,000 solar luminosities, substantially contributes to the cooling of the gas. The 3P1-3P0 fine structure line of the O III forbidden line has also been detected at 88 microns toward Sgr A West, coming from high density ionized gas.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 276; 551-559
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  • 3
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    Monte Carlo shock-like solutions to the Boltzmann equation with collective scattering (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The results of Monte Carlo simulations of steady state shocks generated by a collision operator that isotropizes the particles by means of elastic scattering in some locally defined frame of reference are presented. The simulations include both the back reaction of accelerated particles on the inflowing plasma and the free escape of high-energy particles from finite shocks. Energetic particles are found to be naturally extracted out of the background plasma by the shock process with an efficiency in good quantitative agreement with an earlier analytic approximation (Eichler, 1983 and 1984) and observations (Gosling et al., 1981) of the entire particle spectrum at a quasi-parallel interplanetary shock. The analytic approximation, which allows a self-consistent determination of the effective adiabatic index of the shocked gas, is used to calculate the overall acceleration efficiency and particle spectrum for cases where ultrarelativistic energies are obtained. It is found that shocks of the strength necessary to produce galactic cosmic rays put approximately 15 percent of the shock energy into relativistic particles.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 286; 691-701
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  • 4
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    Submillimeter wavelength survey of the galactic plane from l = -5 deg to l = +62 deg - Structure and energetics of the inner disk (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Observational results are presented from a new large-scale survey of the first quadrant of the galactic plane at wavelengths of 150, 250, and 300 microns, with a 10 x 10 arcmin beam. The emission detected in the survey arises from compact sources, most of which are identified with known peaks of 5 GHz or CO emission, or both, and from an underlying diffuse background with a typical angular width of about 0.9 deg (FWHM) which accounts for most of the emission. A total of 80 prominent discrete sources are identified and characterized, of which about half have not previously been reported at far-infrared wavelengths. The total infrared luminosity within the solar circle is about 1 to 2 x 10 to the 10th solar luminosity, and is probably emitted by dust that resides in molecular clouds.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 285; 74-88
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  • 5
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    The formation of stellar systems from interstellar molecular clouds (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The observational and theoretical study of regions of continuing star formation promises greater insight into the physical conditions and events associated with the formation of the solar system, and elucidates the role played by star formation in the evolutionary cycle which seems to dominate interstellar material's processing by successive generations of stars in the spiral galaxies. Novel astronomical methods incorporated by the new facilities scheduled for development in the 1980s may yield substantial advancements in star formation process theory; most significant among these efforts will be the identification and examination of the elusive protostellar collapse phase of both star and planetary system formation.
    Keywords: ASTROPHYSICS
    Type: Science (ISSN 0036-8075); 224; 823-830
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  • 6
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    Submilliarcsecond VLBI Observations of the Close Pair GC 1342+662 and GC 1342+663 (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-11
    Description: Differential VLBI was simultaneously performed on the source pair GC 1342+662 and GC 1342+663 (4.4-arcminute separation) using S-band on the Goldstone/Madrid baseline. These measurements were acquired on two separate observing sessions: 30 December 1982 and 14 May 1983. The change in separation of GC 1342+662 relative to GC 1342+663 between the two epochs was 0.03 + or 0.08 milliarcsecond. The differences of the relative position measurements between epochs of GC 1342+662 relative to GC 1342+663 were -0.29 + or - 0.05 milliarcsecond in right ascension and 0.14 + or - 0.09 milliarcsecond in declination. These measurements demonstrate submilliarcsecond accuracy and repeatability. The discrepancies outside of the formal uncertainties could be attributed to the intrinsic properties of the sources such as structure and to a lesser probability, proper motion. These discrepancies could also be attributed to excursions in UT1-UTC of about four times the quoted BIH uncertainty.
    Keywords: ASTROPHYSICS
    Type: The Telecommun. and Data Acquisition Rept.; p 12-18
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  • 7
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    Tests of general relativity using Starprobe radio metric tracking data (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Previously cited in issue 12, p. 1992, Accession no. A82-27092
    Keywords: ASTROPHYSICS
    Type: Journal of Guidance, Control, and Dynamics (ISSN 0731-5090); 7; 36-44
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  • 8
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    X-ray observations of gamma-ray burst source locations (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Keywords: ASTROPHYSICS
    Type: Physica Scripta (ISSN 0031-8949); T7; 127
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  • 9
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    Shock acceleration in active galactic nuclei and quasars (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A model of spherical accretion on a massive black hole as the energy source for active galactic nuclei and quasars is considered. According to the model, the kinetic energy of the infalling material is randomized by a collisionless shock around the black hole. Relativistic protons are produced with high efficiency via first order Fermi shock acceleration and, because their kinetic energy is much larger than the gravitational potential energy, do not fall into the black hole. The model can produce relativistic particles with flat spectra needed to account for the radiation from these sources, including their broad band spectral characteristics. Since all electrons are secondaries resulting from proton-proton collisions throughout the volume of the source, this model avoids the Compton catastrophe problem.
    Keywords: ASTROPHYSICS
    Type: Max-Planck Inst. fuer Physik und Astrophysik X-Ray and UV Emission from Active Galactic Nuclei; p 185-187
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  • 10
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    Pioneer 10 and Voyager observations of the interstellar medium in scattered emission of the He584 A and H Lya 1216 A lines (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The combination of Pioneer photometric and Voyager spectrometric observations of EUV interstellar-interplanetary emissions in the region beyond 5 A was applied to a determination of atomic hydrogen and helium densities. These density estimates obtained from direct measurement of scattered radiation depend on absolute calibration of the instruments in the same way as other earlier determinations based on the same method. However, the spacecraft data were combined with daily full sun averages of the H Lyman 1216 A line obtained by the Solar Mesospheric Explorer satellite to obtain a measure of atomic hydrogen density independent of instrument absolute calibration. The method depends on observations of long and short term temporal variability of the solar line over a one year period, and the fact that the ISM is optically thick. The density estimates from preliminary work on these observations are H = 0.12 cu cm and H = .016 cu cm, giving a density ratio close to the cosmic abundance value in contrast to some earlier results indicating a depletion of atomic hydrogen. Estimates were obtained of galactic background emissions in the signals of both spacecraft.
    Keywords: ASTROPHYSICS
    Type: NASA-CR-173931 , NAS 1.26:173931
    Format: application/pdf
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