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  • ASTRONOMY  (60)
  • GENERAL
  • 1975-1979  (62)
  • 1955-1959
  • 1979  (62)
  • 1
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    Direct determination of asteroid diameters from occultation observations (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Of the available earth-based techniques for determining asteroid diameters, observation of stellar occultations involving asteroids is clearly the most direct. The high degree of accuracy achievable by this method has already been demonstrated in the case of Pallas, whose mean diameter has been measured with a standard error of plus or minus 2%. In this paper the problems, results and prospects of the stellar occultation technique are reviewed. It is shown that, with the use of a network of small, portable telescopes, the method is currently applicable to a large number of asteroids. The best results can be expected for asteroids of large angular diameter and regular shape. The potential of lunar occultation observations for asteroid diameter measurements is also briefly discussed.
    Keywords: ASTRONOMY
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  • 2
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    Forbidden Fe X and forbidden Fe XIV emission from Puppis A and other supernova remnants (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Measurements of Fe XIV 5303-A and Fe X 6374-A forbidden emission from several supernova remnants are reported, and their relation to X-ray observations is discussed. The brightest Fe XIV forbidden-emission region in Puppis A is interpreted as being the result of the supernova shock wave's interacting with a dense cloud in the interstellar medium.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 228
    Format: text
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  • 3
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    Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: This paper discusses effective temperatures, angular diameters, distances, and linear diameters that have been determined for 160 O and B stars on the basis of published UV spectrophotometry, visible and near-IR intermediate-band photometry, and model-atmosphere fluxes. The results are compared with previous measurements and calculations for main-sequence and giant O and B stars. It is found that: (1) the flux effective temperatures of O and B supergiants are systematically lower than those of main-sequence and giant stars of the same subtype; (2) the effective temperatures and radii of Beta Cep stars are the same as those of nonvariable stars of the same spectral type; (3) Be stars that do not have two Balmer jumps have effective temperatures very similar to those of normal B stars of the same subtype; (4) O and B stars increase in size from the main sequence to supergiants; and (5) late B supergiants are approximately twice as large as O9 supergiants.
    Keywords: ASTRONOMY
    Type: Royal Astronomical Society; vol. 189
    Format: text
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  • 4
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    A comparison of high resolution radio and far-infrared maps of M 17 (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: New 3.5-cm radio and 69-micron far-infrared maps of M17, both made with an angular resolution of about 1.5 arcmin, are presented. Each map has three distinct maxima. Two of the maxima on the far-IR map agree in position with the corresponding maxima on the radio map. However, the positions of the brightest peak in the radio and far-infrared maps, located in the SW part of M17, differ by 4.6 + or - 2.2 s in right ascension and +44 + or - 20 sec in declination, with the far-infrared peak lying between the radio peak and the dense molecular cloud southwest of the H II region. It is believed that the positional offset of the radio and far-infrared peak is physically significant. The origin of the far-infrared radiation appears to be thermal emission from dust at the interface of the ionized gas and molecular cloud. This interface region is probably heated by radiation from the H II region.
    Keywords: ASTRONOMY
    Type: Astronomy and Astrophysics; 76; 1, Ju; June 197
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  • 5
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    Near-infrared observations of a new molecular feature in IRC + 10216 (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: This letter presents a spectrum of IRC + 10216 in the 3000-4400-kayser region at 9-kayser resolution. A molecular feature at 3400-3600 kaysers has been detected which is attributed to an unspecified N-H bonded molecule; the feature appears to be variable in phase with the infrared light curve. Evidence is given for temperature variations of the emitting dust shell in phase with the infrared light curve. The results suggest that the variability of the molecular feature is due to reversible dissociation of the responsible molecule, which could occur at the higher temperatures accompanying the maxima of the light curve.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 231
    Format: text
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  • 6
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    The detection of an optical burst coincident with an X-ray burst from MXB 1837 + 05 /Ser X-1/ (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The detection of a simultaneous optical and X-ray burst from MXB 1837 + 05 (4U 1837 + 04 = Ser X-1) is reported. A similar detection was made earlier from MXB 1735-44. These are the only two burst sources that have been optically observed (simultaneous with X-ray observations) at a high level of sensitivity. Therefore, it may well be that optical bursts commonly accompany X-ray bursts. The relative timing and flux ratio of the optical and X-ray bursts imply that the optical radiation is probably reemission from X-ray-heated matter within 1-2 light seconds of the X-ray source and no more than a few light seconds in extent. This matter may be in an accretion disk around the X-ray source or possibly in the atmosphere of a dwarf companion.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 233
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  • 7
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    The brightness distribution of IRC +10216 at 11 microns (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The brightness distribution of IRC +10216 at a wavelength of 11 microns was measured in detail using a spatial interferometer. This brightness distribution appears to have azimuthal symmetry; an upper limit of 1.1 may be set to the ellipticity at 11 microns if the object has a major axis oriented either along or perpendicular to the major axis of the optical image. The radial distribution shows both compact and extended emission. The extended component, which is due to thermal emission from circumstellar dust, contributes 91% of the total flux and has a 1/e diameter of 0.90 minutes. The tapered shape of this component is consistent with a l/r squared dust density dependence. The compact component is unresolved (less than 0.2 minutes in diameter) and represents emission from the central star seen through the circumstellar envelope.
    Keywords: ASTRONOMY
    Type: NASA-CR-157646
    Format: application/pdf
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  • 8
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    Current results and developments in astrometric VLBI at the Jet Propulsion Laboratory (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Jet Propulsion Laboratory's program of astrometric VLBI as one element of a navigation system for interplanetary spacecraft includes developing a radioastrometric source catalog, and a catalog of positions of compact extragalactic radio sources correct to about 0.01 arc sec. The three (64 m) antenna complexes of the Deep Space Network in Spain, Australia, and the U.S. are involved, each equipped to receive simultaneously at wavelengths of 13 and 3.6 cm with total system temperatures of about 20-25 K at both wavelengths. The program is to provide precise values of parameters used in navigational computations, including UT1 accurate to about 0.001s, and current values of polar motion to 30 cm. Bandwidth synthesis methods were applied to measure delays as well as rates regarding source positions derived from observations using the Mark II VLBI recording system which has a sampling rate of four million bits per second.
    Keywords: ASTRONOMY
    Type: Modern astrometry; Sep 11, 1978 - Sep 14, 1978; Vienna; Austria
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  • 9
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    Influence of alignment and surface defects on the performance of X-ray telescopes (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The effects of misalignment and surface deformations on the image quality of a grazing incidence telescope with six nested subsystems are investigated. The axial rms-spot size serves as a measure for the image quality. The surface deformations are simulated by ellipsoidal and sinusoidal deviations from the ideal surface. Misalignments are tilts, decenters, and despaces of the individual elements. The effects of each type of defect are analyzed in a single two-element system. The full nested system is then analyzed in the presence of all possible defects on all 12 elements, whereby the magnitude of the defects is randomized within a given upper limit.
    Keywords: ASTRONOMY
    Type: Space optics: Imaging X-ray optics workshop; May 22, 1979 - May 24, 1979; Huntsville, AL
    Format: text
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  • 10
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    Cosmic X-ray telescope for ARIES rocket observations (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A rocket-borne Wolter Type I X-ray telescope having a focal length of 2.3m, an entrance aperture of 66cm and a geometrical area of 380cm2 is nearing completion. The telescope mirrors are formed by diamond turning their figures into forged aluminum substrates of 5083 alloy. These diamond-turned substrates are subsequently plated with a thin coating of electroless nickel and polished to obtain the final X-ray reflecting surfaces. Details of the rocket payload, the X-ray telescope, its calculated response and the experience gained in selecting the mirror substrate alloy are discussed and the current status of the telescope is reviewed.
    Keywords: ASTRONOMY
    Type: Space optics: Imaging X-ray optics workshop; May 22, 1979 - May 24, 1979; Huntsville, AL
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