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  • ASTROPHYSICS  (566)
  • SPACE SCIENCES
  • 1980-1984  (566)
  • 1980  (566)
  • 1
    Publication Date: 2019-08-28
    Description: X-ray observations of the first major outburst of the classical transient X-ray source Centaurus X-4 since its discovery in 1969 are presented. The observations were obtained in May, 1979, with the all-sky monitor on board Ariel 5. The flare light curve is shown to exhibit many of the characteristics of other transients, including a double-peaked maximum, as well as significant, apparently random, variations and a lower peak flux and shorter duration than the 1969 event. Application of a standard epoch-folding technique to data corrected for linear decay trends indicates a possible source modulation at 0.3415 days (8.2 hours). Comparison of the results with previous other data on Cen X-4 and the characteristics of the soft X-ray transients allows a total X-ray output of approximately 3 x 10 to the 43rd ergs to be estimated, and reveals the duration and decay time of the 1979 Cen X-4 outburst to be the shortest yet observed from soft X-ray transients. The observations are explained in terms of episodic mass exchange from a late-type dwarf onto a neutron star companion in a relatively close binary system.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
    Format: text
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  • 2
    Publication Date: 2019-08-28
    Description: The problem of selecting the optimal algorithm of filtration and the optimal composition of the measurements is examined assuming that the precise values of the mathematical expectancy and the matrix of covariation of errors are unknown. It is demonstrated that the optimal algorithm of filtration may be utilized for making some parameters more precise (for example, the parameters of the gravitational fields) after preliminary determination of the elements of the orbit by a simpler method of processing (for example, the method of least squares).
    Keywords: ASTROPHYSICS
    Type: NASA-TM-76237
    Format: application/pdf
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  • 3
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    In:  CASI
    Publication Date: 2019-08-28
    Keywords: ASTROPHYSICS
    Type: NASA-NEWS-RELEASE-80-3 , P80-10003
    Format: application/pdf
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  • 4
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    In:  CASI
    Publication Date: 2019-08-28
    Description: The nature of type 1 supernovae (SN 1) is discussed through a comparison of observational evidence and theoretical perspectives relating to both type 1 and 2 supernovae. In particular two hypotheses relating to SN 1 phenomenon are examined: the first proposing that SN 1 are components of binary systems in which, at a comparatively late stage of evolution, overflow of the mass occurs; the second considers pre-SN 1 to be recently evolved stars with a mass greater than 1.4 solar mass (white dwarfs). In addition, an explanation of the reduced frequency of flares of SN 1 in spiral galaxies as related to that in elliptical galaxies is presented.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-76238 , PR-395
    Format: application/pdf
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  • 5
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    In:  CASI
    Publication Date: 2019-08-28
    Keywords: ASTROPHYSICS
    Type: NASA-NEWS-RELEASE-80-24 , P80-10023
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  • 6
    Publication Date: 2019-08-28
    Description: Radial velocity variations are demonstrated for four southern RS CVn candidates: HD 39937, 101379, 155555, and 174429. The period of HD 155555 appears to have decreased by about one part in 100,000 over the past 18 yr. In addition, high-resolution observations of the Ca II H and K profiles and the Mg II 2800-A emission doublet are presented. These enhance the likelihood of these being RS CVn objects. Radial velocity data for 15 other late-type bright field stars are presented. Some of these were observed by Copernicus and may exhibit unusual chromospheres, while the rest lack radial velocity information as tabulated in the Bright Star Catalog. All velocity measures have been corrected to the IAU heliocentric system.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal; 85; July 198
    Format: text
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  • 7
    Publication Date: 2019-08-28
    Description: The structural evolution of variable radio sources is examined in the Hedgehog model. It is shown that the time evolution of the angular separation of two components is described by the ellipse equation.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-76209 , PR-325
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  • 8
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    In:  CASI
    Publication Date: 2019-08-13
    Description: The book ""Tested on Oneself'' is summarized and reviewed. Topics in the field of space flight and aerospace medicine are addressed.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-75736
    Format: application/pdf
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  • 9
    Publication Date: 2019-08-13
    Description: Lines of the first three states of ionization of mercury have been observed in Mu Leporis and Chi Lupi using the Copernicus satellite. Lines of Hg II and Hg III have been observed in Alpha Andromedae. There appears to be an absorption feature at every wavelength where there is expected to be a mercury line. The presence of all three states of ionization is likely in Mu Lep and Chi Lup. The relative equivalent widths of the lines of the various states of ionization do not depend on the effective temperature of the stars, in contradiction to what is expected if mercury were uniformly distributed in the atmosphere. It is, however, expected if mercury has been concentrated, by diffusion, in a thin layer, where the radiative forces just equal the gravitational forces on mercury. That mercury should be so concentrated is also required by the explanation of the mercury isotope anomaly proposed by Michaud, Reeves, and Charland.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 239
    Format: text
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  • 10
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    In:  Other Sources
    Publication Date: 2019-07-13
    Description: Two somewhat disjoint scenarios for Type I supernovae are presented. One scenario is based on mass accretion by a white dwarf in a binary system, while the other involves a star of 8 to 10 solar masses which may or may not be a solitary star. In spite of the apparent dissimilarities of the two models, it may be that each occurs to some extent in nature, for they both share the possibility of producing substantial quantities of Ni-56 and explosions in stars devoid of hydrogen envelopes. It is concluded that these are two properties that must be shared by any viable Type I model.
    Keywords: ASTROPHYSICS
    Type: In: Type I supernovae; Mar 17, 1980 - Mar 19, 1980; Austin, TX
    Format: text
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