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  • 1
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    Observations of the 4.8-hour variations of Cygnus X-3 above 7 keV from the OSO-7 (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Results of observations made (during the period from June 30 to July 5, 1972) of Cyg X-3 with the UCSD OSO-7 X-ray telescope in the range from about 7 to 100 keV. The 4.8-hour variation was detected in the 6.6-21.2 keV range, and the ratio of high intensity to mean intensity was 1.52 plus or minus 0.16. In the 21.2-97.8 keV range no 4.8-hour variation in phase with the 6.6-21.2 keV variation could be detected, and the ratio at the phase of high intensity to the mean intensity was 0.6 plus or minus 0.4.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 192; Sept. 15
    Format: text
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  • 2
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    Upper limit to the X-ray flux from the supernova in NGC 5253 above 7 keV from the OSO-7 (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 193; Nov. 1
    Format: text
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  • 3
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    The HEAO 1 A-4 catalog of high-energy X-ray sources (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Results are reported from an all-sky survey carried out at high X-ray energies (13-180 keV) from August 1977 until January 1979 using data obtained with the UCSD/MIT Hard X-Ray and Low-Energy Gamma-Ray Instrument on the HEAO 1 satellite. Visual displays are presented which indicate qualitatively the location, intensities, and time variability of the detected high-energy X-ray sources. A model-dependent procedure for the quantitative analysis of the sky survey data is described. The results of this procedure are presented in tabular form and include fitted count rates in four broad energy bands for about 70 sources. All sources which were detected at a level of statistical significance of not less than about 6 sigma were clearly evident in the visual displays of sky survey data. The survey is therefore complete, except in regions of source confusion, down to an intensity level of about 1/75 of the Crab Nebula in the 13-80 keV band. Forty-four sources were detected in the 40-80 keV energy band, and 14 were detected in the 80-180 keV band. Although most of the detected sources are galactic, seven are extragalactic.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 54; 581-617
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  • 4
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    UCSD OSO-7 observations of the hard X-ray spectrum and variability of Centaurus A (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Results are reported for four X-ray scans of the region containing Cen A. It is found that the X-ray source had a hard number spectrum (spectral index of -1.2) during these observations and that the intensity in the range from 10 to 100 keV apparently increased by 230% with no detectable change in spectral shape between two observations 210 days apart. Either a Compton-synchrotron mechanism or thermal bremsstrahlung at any temperature greater than 200 keV is suggested as the source of the X-rays. It is noted that the present observations, together with a similar detection of another galaxy, may establish a distinct class of extragalactic X-ray objects with flat and highly absorbed spectra.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 206; May 15
    Format: text
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  • 5
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    Long-term variations of Cygnus X-1 observed with the HEAO-3 high resolution gamma-ray spectrometer (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The HEAO-3 high resolution gamma-ray spectrometer observed Cygnus X-1 for a total of 148 days between Sept. 27, 1979 and June 2, 1980. During this period, an upward and a downward transition of the hard X-ray flux in the 48-300 keV range were observed. The time scales of these transitions were long (20-50 days) compared with previous observation of the same source. The second, downward, transition was anticorrelated with the 1-12 keV flux, a type of behavior observed previously; however, the upward transition was accompanied by an upward transition in the low-energy X-ray flux, a result contrary to previous experience.
    Keywords: ASTRONOMY
    Type: International Cosmic Ray Conference; Jul 13, 1981 - Jul 25, 1981; Paris; France
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  • 6
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    Spectrum and variation of gamma-ray emission from the galactic center region (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Continuum emission at 60-300 keV from the galactic center region was observed to decrease in intensity by 45 percent and to show a spectrum steepening between fall 1979 and spring 1980. At the same time 511 keV positron annihilation radiation decreased by a comparable fraction. No variations over shorter time scales were detected. The observations are consistent with a model where positrons and hard X-rays are produced in an electromagnetic cascade near a massive black hole.
    Keywords: ASTRONOMY
    Type: International Cosmic Ray Conference; Jul 13, 1981 - Jul 25, 1981; Paris; France
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  • 7
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    16 November 1979 gamma-ray bursts observed with HEAO-3 High-Resolution Gamma-Ray Spectrometer (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: On 1979 November 16, two gamma-ray bursts were observed by the High-Resolution Gamma-Ray Spectrometer on HEAO-3. The first event occurred at 14:16:41 U.T. and lasted about eight seconds. This event was detected only by the instrument's five CsI anticoincidence shield pieces. The second event occurred 61 sec later, at 14:17:42, and lasted about 18 sec. This event was clearly detected by the high-resolution germanium detectors. Because of the close temporal coincidence of the two events, the possibility is considered that both events originated from one celestial source, and that the scanning motion of HEAO-3 (nominal spin period 20 min) excluded the first from the approximately 30 deg FWHM field of view of the germanium detectors but included the second. Directional information from the relative response of the five shield pieces and the earth occultation constraint are all consistent with this interpretation and suggest a source location near RA equals 10 hr, Dec equals 45 deg. No significant spectral features appear in the high-resolution data from the second burst.
    Keywords: ASTRONOMY
    Type: International Cosmic Ray Conference; Jul 13, 1981 - Jul 25, 1981; Paris; France
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  • 8
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    Simultaneous radio and X-ray observations of the X-ray burst source MXB 1636-53 (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: On June 17, 1977, the X-ray burst source MXB 1636-53 was simultaneously monitored for about 4 hr with the Parkes 64-m radio telescope at a frequency of 14.7 GHz and the SAS 3 X-ray satellite (1.3-12 keV). One X-ray burst was observed; an upper limit (2 sigmas) of 200 mJy is reported for any radio burst coincident with the X-ray event. During the X-ray burst the radio/X-ray time-integrated flux ratio was no more than 375 with a 90 percent confidence. An upper limit (2 sigmas) of 22 mJy was determined for any steady 14.7-GHz source coincident with the X-ray position.
    Keywords: ASTRONOMY
    Type: Royal Astronomical Society; vol. 187
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