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  • 1
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    Soft X-rays from Her X-1 during the off phase (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Weak 0.28-keV radiation was observed from Her X-1 5 days before turn-on in the 35 day cycle. The observations were made from an Aerobee rocket. The 0.28-keV intensity is about 1/25 that observed during the on phase. Some evidence for X-rays above 1 keV is also present, and it is possible that the spectrum is different only in intensity from the spectrum in the on phase. The radiation may be X-rays from the vicinity of the neutron star, scattered by ionized material in the inner accretion disk, or may be thermal radiation from the inner accretion disk, or both.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 127-139
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  • 2
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    Soft X-ray emission from a newly discovered supernova remnant in Cygnus (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 222
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  • 3
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    Test of the decaying dark matter hypothesis using the Hopkins Ultraviolet Telescope (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Sciama's hypothesis that the dark matter associated with galaxies, galaxy clusters, and the intergalactic medium consists of tau neutrinos of rest mass 28-30 eV whose decay generates ultraviolet photons of energy roughly 14-15 eV, has been tested using the Hopkins Ultraviolet Telescope flows aboard the Space Shuttle Columbia. A straightforward application of Sciama's model predicts that a spectral line from neutrino decay photons should be observed from the rich galaxy cluster Abell 665 with an SNR of about 30. No such emission was detected. For neutrinos in the mass range 27.2-32.1 eV, the observations set a lower lifetime limit significantly greater than Sciama's model requires.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 351; 128-130
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  • 4
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    Modeling of Lyman edge features in accretion disk spectra (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: We consider two possibilities which can change the spectral shape of the Lyman-limit region in the radiation emitted by the accretion disks of Active Galactic Nuclei (AGN) and quasars. One is the effect produced by the strong gravitational field of the black hole, and the other is Comptonization of the emitted disk spectrum by a surrounding hot corona. We present synthesized spectra in the region of the Lyman limit for optically thick, geometrically thin accretion disk models incorporating the above two effects.
    Keywords: ASTROPHYSICS
    Type: In: Testing the AGN paradigm; Proceedings of the 2nd Annual Topical Astrophysics Conference, Univ. of Maryland, College Park, Oct. 14-16, 1991 (A93-29801 11-90); p. 159-162.
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  • 5
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    HUT observations of carbon monoxide in the coma of Comet Levy (1990c) (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Observations of comet Levy (1990c) were made with the Hopkins Ultraviolet Telescope during the Astro-1 Space Shuttle mission on 10 Dec. 1990. The spectrum, covering the wavelength range 415 to 1850 A at a spectral emission of 3 A (in first order), shows the presence of carbon monoxide and atomic hydrogen, carbon, and sulfur in the coma. Aside from H I Lyman-beta, no cometary features are detected below 1200 A, although cometary O I and O II would be masked by the same emissions present in the day airglow spectrum. The 9.4 x 116 arcsec aperture corresponds to 12,000 x 148,000 km at the comet. The derived production rate of CO relative to water, 0.13 + or - 0.02, compared with the same ratio derived from IUE observations (made in Sep. 1990) which sample a much smaller region of the coma, 0.04 + or - 0.01, suggests the presence of an extended source of CO, as was found in comet Halley. Upper limits on Ne and Ar abundance are within an order of magnitude or solar abundances.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Abstracts for the International Conference on Asteroids, Comets, Meteors 1991; p 60
    Format: application/pdf
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  • 6
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    Optical and X-ray observations of 3U 0614+09 (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Based on positional agreement, ultraviolet excess, and spectroscopic peculiarity, the identification of the X-ray source 3U 0614+09 with a faint blue star, previously suggested by Murdin et al. (1974) as a candidate, is established. Four days of X-ray observations at 1-3 A failed to show evidence for significant variability or eclipses. The possibility that this object may be very similar to Sco X-1, but at a distance of 4-8 kpc, is discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 193; Oct. 1
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  • 7
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    Ultraviolet spectrum of quasi-stellar object 3C273 (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The first direct observation of the ultraviolet spectrum of a quasi-stellar object (QSO) has been made with a rocket-borne telescope. The emission line spectrum of 3C273 is similar to the spectra of high-redshift QSOs, but no absorption is observed. The results provide important new constraints on theoretical models of QSOs, place a severe limit on the density of neutral hydrogen in the intergalactic medium, and suggest a cosmological origin for much of the absorption seen in high-redshift QSOs. Comparison of the ultraviolet spectrophotometry of low- and high-redshift QSOs suggests that the universe is closed, with a deceleration parameter of about 1.
    Keywords: ASTROPHYSICS
    Type: Nature; 269; Sept. 15
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  • 8
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    Soft X-ray sources and supernova remnants in Cygnus - Rocket and Apollo-Soyuz results (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Soft X-ray observations of the Cygnus region obtained from proportional counters aboard a rocket and also on the Apollo-Soyuz mission are reported. It is found that Cyg X-6, a source whose flux in confined to the 0.5-2.0-keV band, is a long narrow filament oriented nearly perpendicular to the galactic plane. This feature has a linear dimension greater than or of the order of 150 parsecs, and its spectrum is adequately described by an exponential. Another intense soft source whose flux is also confined to the 0.5-2.0-keV band has been discovered near Gamma Cygni. This source, designed Cyg X-7, has a spectrum characterized by a temperature of 1.5 to 5 million K and a hydrogen column density of at least 10 to the 21st power per sq cm. The possible association of Cyg X-7 with the supernova remnant DR 4 is discussed. An interpretation of this object in terms of the standard adiabatic spherical-shock-wave model yields plausible values for the free paramenters. HB 21, another old supernova remnant, has not been detected as a soft X-ray source.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 215
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  • 9
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    An X-ray survey of BL Lacertae objects (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Results are reported for X-ray observations and nearly simultaneous photographic photometry of four BL Lacertae objects (BL Lac, W Com, ON 325, and AP Lib). The X-ray data were obtained in the band from 2.5 to 7.5 keV using a collimated proportional counter aboard OAO-C. Although none of the sources was detected above background at a statistically significant level, two-sigma upper limits on the X-ray flux incident at earth are given for each object. The photometric data indicate that all four objects were near the faint end of their visibility ranges during the time of the X-ray observations. The X-ray upper limits and B magnitudes are employed to calculate upper limits on the brightness temperatures and angular sizes of the radio synchrotron sources; upper limits on the distances to the objects are obtained from limits on the physical source sizes deduced from the radio variabilities. The strictest distance limit is 240 Mpc for BL Lac. Substantial evidence is noted for variability of ON 325 on a timescale of hours.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 207; July 15
    Format: text
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  • 10
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    Soft X-rays from Hercules X-1 during the 'off' state (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 207; July 1
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