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  • ASTROPHYSICS  (20)
  • 1
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    Ultrasoft X-ray Background Observations of the Local Interstellar Medium (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: Preliminary results from a May 8, 1984 sounding rocket survey of the soft X-ray background are presented. The X-ray detectors are sensitive to X-rays in three soft X-ray bandpasses: 80 to 110 eV, 90 to 188 eV, and 284 to 532 eV (at 20% of peak response). The lowest energy X-rays in this range have a mean free path of order 10 to the 19th power/sq cm and provide information about the local interstellar medium. The count rate in the 80 to 110 eV energy band (the Be band) tracks the 90 to 188 (eV band (the B band) very well, indicating that the same approx. 1 million degree gas that is responsible for the B band emission may be responsible for the bulk of the Be band X-rays as well.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Local Interstellar Medium, No. 81; p 222-225
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  • 2
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    The Nature of the Soft X-ray Emitting Region in the Direction of the North Polar Spur (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: The spatial structure of the X-ray sky in the direction of the North Polar Spur was examined in two energy bands, the B band (0.10 to 0.18 keV) and the C band (0.15 to 0.28 keV). A model with two emitting regions, one local with unabsorbed emission, and the other more distant with emission partially absorbed by spatially varying amounts was investigated. Using the distribution of atomic hydrogen as a measure of absorbing material, this model was used to predict the flux in the direction of the North Polar Spur. The predicted flux was compared to the data obtained from several sounding rocket flights. The derived flux was found to correlate well with the observed data.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Local Interstellar Medium, No. 81; p 211-214
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  • 3
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    Simultaneous X-ray and ultraviolet observations of Epsilon Orionis and Kappa Orionis (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 268; May 1
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  • 4
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    On the origin of the 1 keV diffuse X-ray background (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Soft X-ray sky survey data for high galactic latitudes are used to constrain simple geometric models for the source of the diffuse X-ray background at 1 keV. The intensity maps show two extended and enhanced features, in Eridanus and in the direction of the galactic center, with a relatively uniform sky away from these features and an observed degree of isotropy consistent with a model in which the 0.5-1.2 keV background consists of an isotropic extragalactic component and a thick disk galactic component. A temperature of 2-3 million K and an emission pressure of 0.004 per cm to the 6th pc are derived for the galactic component from an assumed spectrum of 11E to the -1.4 power photons/sq cm s sr keV. While consistent with the data, a local, isotropically distributed source model is shown to pose physical difficulties.
    Keywords: ASTROPHYSICS
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  • 5
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    X-ray observations of Wolf-Rayet stars (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: X-ray observations have been made of a very luminous O8f star, four late WN stars, and eight O VI Wolf-Rayet stars. The X-ray pulse height distributions of the O8f star is analyzed to obtain information on source temperature, emission measure, and location relative to the stellar wind. Only upper limits are obtained for the X-rays from the Wolf-Rayet stars, but for the late WN stars the upper limits are well below the maximum Lx/Lbol detected in earlier surveys. For the O VI stars, the limits, used in conjunction with models for the production of the optical O VI lines, supply information about the excitation conditions in the winds.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 288; 756-763
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  • 6
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    Limits on diffuse X-ray emission from M101 (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Observed limits on diffuse X-ray emission from M101 require that the temperature of any coronal or matrix hot gas which is radiating an appreciable part (10 percent) of the average supernova power be less than 10(5.7)K. Furthermore, the fraction of the galactic plane occupied by hot bubbles similar to the one which apparently surrounds the sun is at most 25 percent in the region between 10 kpc and 20 kpc from the galactic center.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 287; 167-174
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  • 7
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    Limits on soft X-ray flux from distant emission regions (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The all-sky soft X-ray data of McCammon et al., and the new N sub H survey (Stark et al.) was used to place limits on the amount of the soft X-ray diffuse background that can originate beyond the neutral gas of the galactic disk. The X-ray data for two regions of the sky near the galactic poles are shown to be uncorrelated with 21 cm column densities. Most of the observed X-ray flux must therefore originate on the near side of the most distant neutral gas. The results from these regions are consistent with X-ray emission from a locally isotropic, unabsorbed source, but require large variations in the emission of the local region over large angular scales.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 287; 208-218
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  • 8
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    Detection of soft X-ray emission from SMC X-1 (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The observation of 0.25-keV X-rays from SMC X-1 by a soft X-ray experiment aboard OSO 8 is reported. The variable soft X-ray source observed is identified with the hard X-ray source SMC X-1 on the basis of a rather abrupt ending to the emission (fall time about 2.5 hr) at the time SMC X-1 was expected to enter eclipse. A source luminosity of about 5 x 10 to the 38th erg/s in the 0.18-0.28-keV range is derived by assuming a distance of 68 kpc and correcting for attenuation by 3.4 x 10 to the 20th H atoms per sq cm of intervening galactic gas; this luminosity is shown to be about a factor of 40 greater than the observed coincident luminosity in the 0.8-3-keV band. The soft X-ray intensity upon emergence from eclipse is found to be reduced by a factor of at least 20 from the peak intensity prior to eclipse. It is suggested that this asymmetry may reflect a geometry in which the soft X-ray source trails the compact star as in an accretion-stream model.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 228
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  • 9
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    The soft X-ray diffuse background and the structure of the local interstellar medium (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Data from five rocket flights of the Wisconsin soft X-ray sky survey, covering the southern galactic hemisphere with 6.5 deg spatial resolution between 0.1 and 2.0 keV, are presented as intensity maps. Analysis of the data in two energy bands below 0.3 keV is presented here. These low-energy X-rays appear to be emitted from a plasma of about one-million K, the bulk of which is closer to the sun than even the nearest 5 x 10 to the 19th/sq cm of neutral gas. No evidence is found for the presence of nearby small (radius of about 0.6 pc) clouds of cool neutral gas, as has been proposed by McKee and Ostriker (1977). The X-ray measurements are consistent with the small amounts of local neutral material inferred from Lyman-alpha absorption measurements.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 242
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  • 10
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    Observation of features in the soft X-ray background flux (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Two rocket observations of very soft X-ray diffuse intensity show three emission regions of large angular extent. A large portion of the sky as seen with wide angular resolution is mapped. These three regions coincide with broad regions of small column densities of neutral hydrogen. It is suggested that a component of the interstellar medium is very hot and is responsible for the soft X-ray emission and the O VI.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 193; Nov. 1
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