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  • ASTRONOMY  (5)
  • 1975-1979  (5)
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Years
Year
  • 1
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    Soft X-ray spectrum and structure of the supernova remnant G65.2+5.7 (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The HEAO 1 low energy detectors have observed the supernova remnant G65.2+5.7 in the energy range 0.2-2.5 keV. A strong, extended source of X-ray emission is observed coincident with the eastern side of the optical filamentary structure. The characteristic temperature of the emission is in the range 2-3.8 x 10 to the 6th K, and evidence is found for line emission at about 0.8 keV in the X-ray spectrum. These observations imply a shock velocity (425 km/s) and age (about 20,000 yr) that markedly disagree with the estimates from optical and radio observations.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 230
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Discovery of X-ray emission from two southern supernova remnants (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Two soft X-ray sources positionally coincident with the supernova remnants PKS 1209-52 and RCW 103 have been discovered by using the A-2 experiment on HEAO 1. Their measured fluxes are, respectively, about 1.4 x 10 to the -10th erg/cm-sec (0.2-1.0 keV) and about 1.8 x 10 to the -10th erg/cm-sec (0.6-2.0 keV). Spectral data are used to derive physical parameters for each remnant. For PKS 1209-52 the parameters are suggestive of the remnant's being in an advanced evolutionary phase, with shock-heated interstellar material producing the soft X-ray emission. RCW 103, in contrast, is known from radio and optical data to be in an earlier evolutionary phase, and the soft X-ray flux is most likely due to emission originating in a reflected shock wave or in plasma evaporated from shock-heated interstellar clouds.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 230
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Simultaneous X-ray and optical observations of the flaring X-ray source, Aquila A-1 (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: During the summer of 1978 the recurrent transient X-ray source, Aquila X-1, underwent its first major outburst in two years. The results of extensive observations at X-ray and optical wavelengths throughout this event, which lasted for approximately two months are presented. The peak X-ray luminosity was approximately 1.3 times that of the Crab and exhibited spectral dependent flickering on timescales approximately 5 minutes. The observations are interpreted in terms of a standard accretion disk model withparticular emphasis on the similarities to Sco X-1 and other dward X-ray systems, although the transient nature of the system remains unexplained. It was found that Aquila X-1 can be described adequately by the semi-detached Roche lobe model and yields a mass ratio of less than or approximate to 3.5.
    Keywords: ASTRONOMY
    Type: NASA-CR-158849 , UCBSSL-SER-20-ISSUE-34
    Format: application/pdf
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  • 4
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    Spectroscopy of the extreme-ultraviolet source Feige 24 - The binary orbit and the mass of the white dwarf (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Results are reported for coude spectroscopy of the extreme-ultraviolet white dwarf Feige 24. Radial velocities of the H-alpha, He I 5876-A, and He I 6678-A emission lines, and the underlying M-dwarf absorption features, were determined from spectrograms obtained with the Lick 3-m telescope. The velocities show a binary period of 4.239(+ or - 0.0015) days. The emission-line and absorption-line velocities agree in phase, which indicates that the emission lines originate in the atmosphere of the M-dwarf secondary as a result of reprocessing of the EUV radiation. This effect is modeled, and the observed amplitude of the emission-line variability is used to place a lower limit on the orbital inclination. From these and other data it is shown that the mass of the white dwarf lies between 0.46 and 1.24 solar masses. Some possible implications for the evolution of binary stars are briefly discussed.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 223
    Format: text
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  • 5
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    Radio and X-ray observations of NGC 1851 and NGC 1904 (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The globular clusters NGC 1851 and NGC 1904, have been observed simultaneously at radio and X-ray wavelengths with the aid of the Green Bank interferometer and the proportional counter on OAO Copernicus. The combined radio and X-ray observations provided simultaneous coverage of each subject for a total of about one hour. Data concerning the radio frequency observations of the two globular clusters are presented in a table. The X-ray counts per frame are shown in a graph as a function of time, taking into account a five day interval in December 1975.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 212
    Format: text
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