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  • ASTRONOMY  (3)
  • VX Sgr  (1)
  • 1
    ISSN: 1572-946X
    Keywords: VX Sgr ; interferometry ; masers ; mass loss ; dust shells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The circumstellar envelope of the late-type supergiant VX Sagittarii has been studied with VLBI observations of SiO maser emission (J = 1 → 0v = 1) and interferometric observations of mid-infrared dust emission.
    Type of Medium: Electronic Resource
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  • 2
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    In:  Other Sources
    Publication Date: 2011-08-16
    Description: An investigation of the intensity fluctuations of 28 pulsars near 0.4 GHz indicates that spectra of interstellar scintillation are consistent with a Gaussian shape, that scintillation indices are near unity, and that the scintillation bandwidth depends linearly on dispersion measure. Observations at cm wavelengths show that the observer is in the near field of the scattering medium for objects with the lowest dispersion measures, and confirm the steep dependence of correlation bandwidth on dispersion measure found by Sutton (1971). The variations of scattering parameters with dispersion measure may indicate that the rms deviation of thermal electron density on the scale of 10 to the 11th cm grows with path length through the galaxy.
    Keywords: ASTRONOMY
    Type: Astronomy and Astrophysics; 43; 3, Oc; Oct. 197
    Format: text
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  • 3
    Publication Date: 2019-06-27
    Description: An analysis of pulsar average waveforms at radio frequencies from 40 MHz to 15 GHz is presented. The analysis is based on the hypothesis that the observer sees one cut of a hollow-cone beam pattern and that stationary properties of the emission vary over the cone. The distributions of apparent cone widths for different observed forms of the average pulse profiles (single, double/unresolved, double/resolved, triple and multiple) are in modest agreement with a model of a circular hollow-cone beam with random observer-spin axis orientation, a random cone axis-spin axis alignment, and a small range of physical hollow-cone parameters for all objects.
    Keywords: ASTRONOMY
    Type: NASA-TM-X-70917 , X-693-75-138
    Format: application/pdf
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  • 4
    Publication Date: 2011-08-16
    Description: Observations of 12 compact extragalactic sources were made at 2695 and 8085 MHz in order to detect weak intensity fluctuations caused by interstellar scintillation. Pulsar data are used to estimate the parameters of the interstellar medium needed to interpret the measured upper limits in terms of source angular diameters which are much larger than the scintillation cutoff diameter. It is shown that the observed source rms brightness temperatures are less than 10 to the 15th K and 10 to the 14th K at 2695 and 8085 MHz, respectively, making self-absorbed proton-synchroton radiation and high-brightness coherent mechanisms unlikely. If the sources are composed of 'point' components, each source can contain no fewer than 10,000 such components.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 197; Apr. 1
    Format: text
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