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  • ASTROPHYSICS  (3)
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  • 1
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    Optical and infrared pulsations from the HZ Herculis binary system during the 1983 prolonged X-ray low state (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Pulsed infrared and optical flux from HZ Her has been detected during the 1983 prolonged X-ray low state by simultaneous observations with the Lick Observatory Shane 3.1 m and Crossley 91 cm telescopes. The pulsed fluxes in the 1.0-2.5-micron bandpass and the 3200-7500 A bandpass agree in pulse frequency and phase and were measured to be 31 and 13 microJy, respectively. These pulsed fluxes indicate that the reprocessed pulsation spectrum is consistent with optically thin thermal bremsstrahlung radiation with a characteristic temperature of 25,000 K (+25,000; -12,500) which is modulated in intensity. An apparent earth-approaching Doppler velocity of about 65 km/s is observed for these pulsed fluxes; this velocity can be interpreted as pulsed X-ray reprocessing by material in the mass transfer stream between L1 and the outer edge of the accretion disk. Other optical observations made during and before the 1983 prolonged X-ray low state show that the optical pulsations may have been subtly affected by the obscuration responsible for the X-ray low.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 292; 267-275
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Submillisecond optical pulsar in supernova 1987A (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An optical pulsar with frequency f = 1,968,629 Hz has been detected at the location of supernova 1987A in the LMC. The brightness of the pulsed light increased from magnitude 19 to 18 during a 7-hr observation period starting on 18.1 January 1987 UT. The frequency of the pulsar during this same period varied in a nearly sinusoidal manner, with an amplitude of 1.5 x 10 to the -3rd Hz and a period of 8 hr. If this is interpreted as the result of a binary orbit, it suggests that there may be a Jupiter-size object orbiting the pulsar at a distance of 10 to the 6th km.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 338; 234-236
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    NASA TECHNICAL REPORTS
  • 3
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    Limits on an optical pulsar in supernova 1987A (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Since March 1987 the optical flux from supernova 1987A for periodic pulsations has been sought. As of August 1988, after 38 separate observations, no pulsar has been detected. The typical upper limit placed on the pulsed fraction optical light from the supernova is 0.0002, for pulse frequencies in the range 0.03-5000 Hz. The best limit on the pulsed fraction of supernova light is 7 x 10 to the -6th, on January 22, 1988. On August 28, 1988 the faintest limit for the magnitude of the pulsar, dimmer than 20th mag is reached. These limits are based on Fourier transforms of up to 67 million points, covering a range of spindown rates.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 340; L61-L64
    Format: text
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    NASA TECHNICAL REPORTS
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