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  • SPACE SCIENCES  (10)
  • Chemical Engineering  (5)
  • ASTROPHYSICS  (3)
  • 2010-2014
  • 1980-1984  (7)
  • 1970-1974  (11)
  • 1950-1954
  • 1
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    Neutron star envelopes (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: It is pointed out that the separate study of neutron star envelopes is a valuable technique for gaining insights into neutron star cooling calculations. It is shown that, to an excellent approximation, the temperature at the inner boundary of the envelope, T sub b, is a function only of T sub s to the 4th power over g sub s, where T sub s is the effective temperature and g sub s is the surface gravity. This result makes it possible to investigate very simply the effects of general relativity and of opacity changes on the T sub b - T sub s relation and to compare calculations by different workers, even though they use different neutron star models. It is also shown that the most important opacity source for obtaining a reliable T sub b - T sub s relation is the conductive opacity of matter when the ions are liquid. Calculations are presented in which particular attention is given to this region and the best available opacities are used.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 259
    Format: text
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  • 2
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    Structure of neutron star envelopes (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The envelopes of nonmagnetic neutron stars are studied using the best available opacities and equation of state. The general relativistic equations of the structure and evolution of nonmagnetic neutron stars are discussed, and it is shown that they can be reduced to a single equation for calculating the thermal structure of neutron star envelopes. The physical input needed to solve the thermal structure equation is investigated and the numerical results of envelope model calculations are presented. It is shown that the thermal structure of neutron star envelopes is determined by the single parameter T(s) to the 4th/g(s), where T(s) is the effective surface temperature and g(s) the surface gravity of the star. This result is used to derive a number of other scaling relations, and the effects of general relativity on the envelope thermal structure are examined in detail. The results of a sensitivity analysis of the regional opacity needed to obtain a reliable relationship between the temperatures of the inner and outer boundaries of the envelope is presented.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 272; Sept. 1
    Format: text
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  • 3
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    Sensitivity of model calculations to uncertain inputs, with an application to neutron star envelopes (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A method is given for determining the sensitivity of certain types of calculations to the uncertainties in the input physics or model parameters; this method is applicable to problems that involve solutions to coupled, ordinary differential equations. In particular the sensitivity of calculations of the thermal structure of neutron star envelopes to uncertainties in the opacity and equation of state is examined. It is found that the uncertainties in the relationship between the surface and interior temperatures of a neutron star are due almost entirely to the imprecision in the values of the conductive opacity in the region where the ions form a liquid; here the conductive opacity is, for the most part, due to the scattering of electrons from ions.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 204; Aug. 198
    Format: text
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  • 4
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    Synchrotron sources. II - Pulsars and compact extragalactic objects. (1973)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Discussion of some limitations on synchrotron models for optical pulsars and compact extragalactic objects. Using the results of a previous paper, it is shown that several existing models for the pulsar NP 0532 are inconsistent with the measured time variations and polarization of the optical emission. The possibility that the low-frequency falloffs in some extragalactic objects (PKS 2134 + 004, OQ 208, and NGC 1068) could be due to emission from particles with small pitch angles, absorption by a thermal plasma, or synchrotron self-absorption is also considered. It is found that radiation by particles with small pitch angles could explain the radio emission from PKS 2134 + 004 and OQ 208, but this process is inconsistent with the observations of NGC 1068. The absorption interpretations cannot account for the turnover in the spectrum of PKS 2134 + 004.
    Keywords: SPACE SCIENCES
    Type: Astrophysical Journal; 183; July 15
    Format: text
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  • 5
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    Synchrotron sources. I - Extension of theory for small pitch angles. (1973)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Some of the features of synchrotron radiation are examined which occur when relativistic particles move at small pitch angles in a magnetic field. The emission from individual particles is computed. The general properties of the emission from distributions of particles with small pitch angles is discussed, and the emissivities and degrees of polarization for several specific source models are presented. For sources which mainly contain particles with small pitch angles, the degree of circular polarization will normally be high, whereas, if the magnetic field is somewhat irregular, the degree of linear polarization will be small. If the particle distribution also has a low-energy cutoff, the emissivity will vary linearly with frequency at low frequencies.
    Keywords: SPACE SCIENCES
    Type: Astrophysical Journal; 183; July 15
    Format: text
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  • 6
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    Some aspects of cosmic synchrotron sources (1973)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Synchrotron emission is considered from individual particles which have small pitch angles and the general properties of synchrotron sources which mainly contain such particles, as well as the emissivities and degrees of circular polarization for specific source distributions. The limitation of synchrotron source models for optical pulsars and compact extragalactic objects are discussed, and it is shown that several existing models for the pulsar NP 0532 are inconsistent with the measured time variations and polarizations of the optical emission. Discussion is made also of whether the low frequency falloffs in the extragalactic objects PKS 2134 + 004, OQ 208, and NGC 1068 is due to emission from particles with small pitch angles or absorption by a thermal plasma or synchrotron self-absorption. It is concluded that the absorption interpretations cannot account for the turnover in the spectrum of PKS 2134 + 004. Measurements of polarization, angular structure, and X-ray flux are also described.
    Keywords: SPACE SCIENCES
    Type: NASA-CR-131526 , SUIPR-435
    Format: application/pdf
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  • 7
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    Oxygen and silicon isotope ratios of lunar rock 12013 (1970)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Apollo 12 lunar rock 12013 oxygen 18 and silicon 30 ratios, comparing to terrestrial basalts and gabbros, Apollo 11 rocks and oceanic rhyolite obsidians
    Keywords: SPACE SCIENCES
    Type: ; ADEMIE DES SCIENCES
    Format: text
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  • 8
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    Oxygen and silicon isotope ratios of the Luna 20 soil. (1973)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: SPACE SCIENCES
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  • 9
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    3C 120, BL Lacertae, and OJ 287 - Coordinated optical, infrared, and radio observations of intraday variability. (1972)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Keywords: SPACE SCIENCES
    Type: Astrophysical Journal; 178; Dec. 1
    Format: text
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  • 10
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    O-18/O-16 and Si-30/Si-28 studies of some Apollo 15, 16, and 17 samples (1973)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A study of lunar rock samples from eight sites on the near side of the moon showed oxygen isotope abundance variations much smaller than those in meteorites and earth material. The grain-surface coatings of the lunar fines were found to be generally depleted in oxygen relative to silicon. The lunar soils, on the other hand, were somewhat richer in both O18 and Si30 than the lunar crystalline rock.
    Keywords: SPACE SCIENCES
    Type: Lunar Science Conference; Mar 05, 1973 - Mar 08, 1973; Houston, TX
    Format: text
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