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  • 1
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    VLBI observations of the nucleus of the radio galaxy Cygnus A (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The central component of the radio galaxy Cygnus A has been observed in several (very long baseline interferometry) experiments between 1975 and 1979, and the results have been combined to derive a model for the brightness distribution. Some 65% of the nuclear emission appears to come from a compact core. The remaining flux density comes from a more extended region (or regions) up to 4 or 5 mas away lying along a position angle near 100 deg, which is close to that of the extended lobes. Evidence that compact central components reflect the collimation and transport of energy to the outer lobes of radio galaxies is discussed, and several interpretations of the observed asymmetries are considered.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 97; 1, Ap; Apr. 198
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  • 2
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    Cyg X-1 - A massive neutron star (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The expected X-ray emission from Cyg X-1, considered a massive neutron star (8-15 solar masses) according to some gravity theories, is studied within the framework of Rosen's bimetric gravity theory (1973, 1974). It is shown that in such massive neutron stars, the innermost stable orbit lies far outside the star surface, and therefore the X-ray spectrum consists of two components: a soft one emitted from a cold accretion disk and a hard one emitted by the matter striking the neutron star surface after spiraling down freely from the disk. The proposed model is shown to be in good agreement with the observed luminosities. The model predicts a surface gravitational redshift of 3.16 which could be tested by the future X- and gamma-ray detectors.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 97; 2, Ap; Apr. 198
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  • 3
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    On stellar wind accretion in widely separated X-ray binaries, and the nature of 4U0115+63 (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Widely separated, eccentric pulsating X-ray binaries are shown to be appropriate systems for studying the basic properties of stellar wind accretion. They are free from the complications encountered in closed binaries, where the optical star nearly fills its critical lobe (Avni, 1977). A framework of four observational tests was set up to study the characteristics of wind accretion, and to distinguish between different models of wind acceleration. The tests are applied to the source 4U0115+63, and the accretion process is discussed in both its quiescent states, and during its transient high luminosity outbursts. For the quiescent steady state, two wind profiles, determined from observational data, are compared (Barlow-Lohen, 1977; Castor et al., 1975). The difficulties encountered during the transient high states with respect to the possibility of stellar wind accretion are discussed.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 102; 1, Se; Sept
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  • 4
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    On the birthrate of galactic supernovae (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The birthrate of galactic supernovae is estimated in three different ways. The three ranges overlap, and it is suggested that 70 + or - 35 yr represents a more realistic estimate of the rate than some that have previously been made. The galactic supernova remnants and their observed systematic brightness gradients perpendicular to the galactic plane imply a scale height of about 200 pc for the remnant progenitors and a galactic magnetic field scale height of about 300 pc. Long standing anomalies associated with the young remnant AD 1006, the galactic loops, and faint remnants, are accounted for by the brightness gradient effect. This provides firm, independent evidence for the validity of the remnant method of deducing the birthrate of galactic supernovae.
    Keywords: ASTROPHYSICS
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  • 5
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    Intrinsic polarization of SS 433 - An electron scattering model (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A model for the generation of the observed intrinsic linear polarization in the optical radiation from SS 433 due to scattering from free electrons in highly ionized material in a jet or inclined disk is examined and compared with observational data. Expressions for the Stokes parameters of the linear polarization as a function of phase are obtained for a simple jet model in which continuum light from a point source is singly scattered by free electrons located along the jets resulting in strikingly different relations between Q and U at different values of model parameters. Comparison of 30 broadband linear polarization measurements with the model indicates a mean value of rotation axis inclination to the line of sight of 63 deg, which is not inconsistent with X-ray and radio data. The measurements are also compatible with models invoking highly inclined disks or rings with emission arising in regions on opposite sides of a diameter.
    Keywords: ASTROPHYSICS
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  • 6
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    Infrared spectroscopy of interplanetary dust in the laboratory (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A mount containing three crushed chondritic interplanetary dust particles (IDPs) collected in the earth's stratosphere and subjected to infrared spectroscopic measurements shows features near 1000 and 500/cm, suggesting crystalline pyroxene rather than crystalline olivine, amorphous olivine, or meteoritic clay minerals. Chondritic IDP structural diversity and atmospheric heating effects must be considered when comparing this spectrum with interplanetary and cometary dust astrophysical spectra. TEM and infrared observations of one member of the rare subset of IDPs resembling hydrated carbonaceous chondrite matrix material shows a close infrared spectrum resemblance between 4000 and 400/cm to the C2 meteorite Murchison. TEM observations suggest that this class of particles may be used as an atmospheric entry heating-process thermometer.
    Keywords: ASTROPHYSICS
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  • 7
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    On the transport and propagation of relativistic electrons in galaxies (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Analytic solutions to the time-dependent equation describing the transport of relativistic electrons that are being convected and diffused, and may be either gaining or losing energy, are described. The calculations yield a body of solutions from which specific ones can be chosen for the modelling of synchrotron radiation in the Galaxy and in other galaxies. The solutions allow for (1) spatially varying convection velocity; (2) an energy and spatially dependent diffusion coefficient; (3) adiabatic acceleration effects; (4) a term describing spatially dependent synchrotron loss and/or Fermi acceleration; (5) an injection source for the electrons that may be impulsive, steady-state, or variable-injection; (6) a spatial injection or spatially more diffuse source; (7) arbitrary energy dependence of the injection source; and (8) spatial and energy boundaries where the spatial or energy form of the convection, diffusion, and energy supply terms in the basic equation can change character.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series; 47; Sept
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  • 8
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    Mathematical theory of cylindrical isothermal blast waves in a magnetic field (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: An analysis is conducted regarding the properties of cylindrically symmetric self-similar blast waves propagating away from a line source into a medium whose density and magnetic field (with components in both the phi and z directions) both vary as r to the -(omega) power (with omega less than 1) ahead of the blast wave. The main results of the analysis can be divided into two classes, related to a zero azimuthal field and a zero longitudinal field. In the case of the zero longitudinal field it is found that there are no physically acceptable solutions with continuous postshock variations of flow speed and gas density.
    Keywords: ASTROPHYSICS
    Type: Australian Journal of Physics; 34; 3, 19; 1981
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  • 9
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    Measurement of the 0.511 MeV gamma ray line from the Galactic Center (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The detection of the 0.511 MeV electron positron annihilation line coming from the Galactic Center to provide the means to estimate the rate of positron production and to test some theoretical sources of positrons is addressed. The results of the measurements of the 0.511 MeV line flux made with a gamma ray experiment on board a stratospheric balloon are presented. The detector field of view looked at the galactic longitude range -31 deg l(II) +41 deg. The observed flux is 0.0067 (+ or - 0.0005) photons 1/cm(2)5 which is in very good agreement with the expected flux when assuming that the Galactic Center is a line source emitting uniformly.
    Keywords: ASTROPHYSICS
    Type: NASA-CR-164130 , INPE-2004-RPE/286 , Reunion Latino-Am. de la Union de Astron. Intern.,; Merida; Venezuela
    Format: application/pdf
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  • 10
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    Far-infrared properties of dust in the reflection nebula NGC 7023 (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Thermal emission from dust in the reflection nebula NGC 7023 has been observed at wavelengths between 40 and 400 microns. The observed far-infrared emission comes from a region approximately 4 arcmin in diameter and shows spatial structure which correlates well with the distribution of reflected visible radiation. Temperature and optical depth maps indicate that the dust which emits the far-infrared radiation is heated by UV and visual radiation from the central star (HD 200775) and that the dust density increases steeply northwest of the star. The far-infrared data are not consistent with either the spherical or uniform slab geometries used in earlier analyses of optical observations. Comparisons of the far-infrared measurements with optical and UV measurements give a value between 2000 and 5000 for the ratio of extinction efficiency in the UV to that at 125 microns. This value is compared with the results of other observational studies and with theoretical grain models.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 246
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