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  • Other Sources  (2,505)
  • 1980-1984  (2,505)
  • 1983  (2,505)
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  • 1980-1984  (2,505)
Year
  • 1
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    VLBI observations of a radio flare of Circinus X-1 (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: VLBI 2.3 GHz observations of a strong radio flare of the binary star system Circinus X-1 indicate a radio source flaring component angular size of 0.0015-0.015 arcsec. This is equivalent to a linear size of 15-150 AU at the 10 kpc distance of Circinus X-1, although interstellar medium scattering may have enlarged the apparent angular source size. Since the radio source quiescent component, observed prior to the flare, had an angular size greater than 0.2 arcsec (equivalent to more than 2000 AU at 10 kpc), the quiescent radio emission comes from a region much larger than that proposed in recent models for Circinus X-1. The quiescent component appears to be variable on a time scale of years, and is probably fueled by the Circinus X-1 binary system.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 268; May 1
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    VLBI observations of the nucleus of Centaurus A (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: VLBI observations of the nucleus of Centaurus A made at 2.3 GHz on baselines with minimum fringe spacings of 0.15 and 0.0027 arcsec are presented. Results show that the nuclear component is elongated with a maximum extent of approximately 0.05 arcsec which is equivalent to a size of approximately 1 pc at the 5 Mpc distance of Centaurus A. The position angle of the nucleus is found to be 30 + or - 20 degrees, while the ratio of nuclear jet length to width is less than or approximately equal to 20. The nuclear flux density is determined to be 6.8 Jy, while no core component is found with an extent less than or approximately equal to 0.001 (less than or approximately equal to 0.02 pc) with a flux density of greater than or approximately equal to 20 mJy. A model of the Centaurus A nucleus composed of at least two components is developed on the basis of these results in conjunction with earlier VLBI and spectral data. The first component is an elongated source of approximately 0.05 arcsec (approximately 1 pc) size which contains most of the 2.3 GHz nuclear flux, while the second component is a source of approximately 0.0005 arcsec (approximately 0.01 pc) size which is nearly completely self-absorbed at 2.3 GHz but strengthens at higher frequencies.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 266
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Far-IR spectroscopy of the galactic center: Neutral and ionized gas in the central 10 pc of the galaxy (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The 3P1 - 3P2 fine structure line emission from neutral atomic oxygen at 63 microns in the vicinity of the galactic center was mapped. The emission is extended over more than 4' (12 pc) along the galactic plane, centered on the position of Sgr A West. The line center velocities show that the O I gas is rotating around the galactic center with an axis close to that of the general galactic rotation, but there appear also to be noncircular motions. The rotational velocity at R is approximately 1 pc corresponds to a mass within the central pc of about 3 x 10(6) solar mass. Between 1 and 6 pc from the center the mass is approximately proportional to radius. The (O I) line probability arises in a predominantly neutral, atomic region immediately outside of the ionized central parsec of out galaxy. Hydrogen densities in the (O I) emitting region are 10(3) to 10(6) cm(-3) and gas temperatures are or = 100 K. The total integrated luminosity radiated in the line is about 10(5) solar luminosity, and is a substantial contribution to the cooling of the gas. Photoelectric heating or heating by ultraviolet excitation of H2 at high densities (10(5) cm(-3)) are promising mechanisms for heating of the gas, but heating due to dissipation of noncircular motions of the gas may be an alternative possibility. The 3P1 - 3P0 fine structure line of (O III) at 88 microns toward Sgr A West was also detected. The (O III) emission comes from high density ionized gas (n 10(4) cm(-3)), and there is no evidence for a medium density region (n 10(3) cm(-3)), such as the ionized halo in Sgr A West deduced from radio observations. This radio halo may be nonthermal, or may consist of many compact, dense clumps of filaments on the inner edges of neutral condensations at R or = 2 pc.
    Keywords: ASTRONOMY
    Type: NASA-CR-166510 , NAS 1.26:166510
    Format: application/pdf
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  • 4
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    Arcsecond positions for milliarcsecond VLBI nuclei of extragalactic radio sources. II - 207 sources (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Time delay and fringe frequency measurements at 2.29 GHz have been obtained with VLBI on baselines of about 10,000 km, in order to determine the positions of milliarcsec nuclei in 207 extragalactic radio sources. Accuracy ranges are estimated to lie between 0.1 and 1.0 arcsec in both right ascension and declination, with all sources having uncertainties of less than 4 arcsec in both coordinates. These sources constitute part of an all-sky VLBI catalog of milliarcsec radio sources, for 752 of which arcsec positions have thus far been determined.
    Keywords: ASTRONOMY
    Type: Astronomical Journal (ISSN 0004-6256); 88; Aug. 198
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  • 5
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    Research in space physics at the University of Iowa, 1982 (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The energetic particles and the electric, magnetic, and electromagnetic fields associated with the Earth, the Sun, the Moon, the planets, comets, and the interplanetary medium are examined. Matters under current investigation are following: energetic particles trapped in the Earth's magnetic field, origin and propagation of very low frequency radio waves and electrostatic, the magnetospheres of Jupiter, Saturn and prospectively Uranus and Neptune, diffusion of energetic particles in Saturn's magnetosphere, radio emissions from Jupiter and Saturn, solar modulation and the heliocentric radial dependence of the intensity of galactic cosmic rays, interplanetary propagation and acceleration of energetic particles, the theory of wave phenomena in turbulent plasmas, and basic wave-particle-chemical processes in the ionospheric plasma.
    Keywords: SPACE SCIENCES (GENERAL)
    Type: NASA-CR-175411 , NAS 1.26:175411
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  • 6
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    Properties of Nickel-Based Hydrogen-Turbine Blades (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: 120 page report presents data on mechanical properties of cast nickelbased alloys for turbine blades operating in hydrogen and steam at high temperatures. Tests on alloys for hydrogen-burning engines of future are described.
    Keywords: MATERIALS
    Type: MFS-25733 , NASA Tech Briefs (ISSN 0145-319X); 7; 1; P. 44
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    A translational registration system for LANDSAT image segments (1983)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The use of satellite images obtained from various dates is essential for crop forecast systems. In order to make possible a multitemporal analysis, it is necessary that images belonging to each acquisition have pixel-wise correspondence. A system developed to obtain, register and record image segments from LANDSAT images in computer compatible tapes is described. The translational registration of the segments is performed by correlating image edges in different acquisitions. The system was constructed for the Burroughs B6800 computer in ALGOL language.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: E83-10373 , NASA-CR-172917 , NAS 1.26:172917 , INPE-2785-PRE/351 , Encontro Nacl. de Automatica Soc. Brasil. de Mat.; Jul 06, 1983 - Jul 13, 1983; Belem, Para
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    NASA TECHNICAL REPORTS
  • 8
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    Observations of NGC 7027 from 5.2 to 7.5 microns - The detection of Ni II and additional dust features (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: NGC 7027 was observed with a multichannel grating spectrometer from 5.2 to 7.5 microns at a spectral resolving power of 120-200. Two new dust emission features are resolved at 5.62 and 6.95 microns, and for the first time the Ni II fine-structure line at 6.64 microns is detected. It is shown that a single molecular dust constituent might account for six of the nine observed dust features between 2 and 14 microns. The strength of the Ni II line indicates either that Ni is not depleted in the neutral gas, or that the line is formed at high density.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 274; 666-670
    Format: text
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  • 9
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    Searches for gamma ray emission from radio pulsars (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Searches were made for pulsed high energy (E greater than 35 MeV) gamma radiation from 43 pulsars using the SAS-2 data base and radio parameters. No positive results were found, and the upper limits are consistent with the concept that gamma ray production efficiency increases with increasing apparent age. Two limits suggest that efficiency cannot be a simple function of apparent age beyond 1,000,000 years. Previously announced in STAR as N83-24463
    Keywords: SPACE RADIATION
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 127; 1, Oc
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  • 10
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    Observations of the 10-micron natural laser emission from the mesospheres of Mars and Venus (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Observations of the total flux and center to limb dependence of the nonthermal emission occurring in the cores of the 9.4 and 10.4 micrometers CO2 bands on Mars are compared to a theoretical model based on this mechanism. The model successfully reproduces the observed center to limb dependence of this emission, to within the limits imposed by the spatial resolution of the observations of Mars and Venus. The observed flux from Mars agrees closely with the prediction of the model; the flux observed from Venus is 74 percent of the flux predicted by the model. This emission is used to obtain the kinetic temperatures of the Martian and Venusian mesospheres. For Mars near 70 km altitude, a rotational temperature analysis using five lines gives T = 135 + or - 20 K. The frequency width of the emission is also analyzed to derive a temperature of 126 + or - 6 K. In the case of the Venusian mesosphere near 109 km, the frequency width of the emission gives T = 204 + or - 10 K.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 55; Sept
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