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  • 1990-1994  (6)
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  • 1
    Electronic Resource
    Electronic Resource
    Imaging high-energy astrophysical sources using Earth occultation (1993)
    [s.l.] : Nature Publishing Group
    Nature 366 (1993), S. 245-247 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In visible-wavelength optics, transform imaging has been described for at least the past 30 years12'13, although it has not seen widespread applications. For high-energy astronomy, transform-imaging processes are reviewed by Caroli et al.1 and by Lei et al.14 The coded-aperture ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/366245a0
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Statistical data analysis for gamma-ray astronomy (1990)
    Springer
    Experimental astronomy 1 (1990), S. 145-163 
    Details
    ISSN: 1572-9508
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Significance testing, parameter estimation and sensitivity calculations for γ-ray telescopes are discussed for single ‘on-off” astronomical observations. Four widely used significance test methods are examined by Monte-Carlo simulations. The Maximum Likelihood Ratio Method is found to consistently over-estimate the significance of an observation by a few percents whereas the Fisher's Exact Test is shown to be slightly conservative and always under-estimates the significance by about the same amount when the reported significance is about 3σ and therefore it is preferred for γ-ray astronomy applications. Two methods for constructing a confidence interval and an upper limit for γ-ray source counts are discussed. It is found that the method based on the Smooth Transformation provides slightly better estimations. A new formula for the calculation of the sensitivity of a γ-ray telescope is presented, in contrast to the widely accepted one, and their statistical meanings are explained in detail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00462037
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  • 3
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    Imaging high-energy astrophysical sources using Earth occultation (1993)
    Springer Nature
    Details
    Publication Date: 1993-11-01
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Springer Nature
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    PAPER CURRENT
  • 4
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    BATSE observations of 3C273 (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The quasar 3C273 has been detected by all instruments on CGRO. The emission from this source is monitored continuously by BATSE using Earth occultation. We present results of a preliminary analysis of BATSE data, including light curves of the 3C273 flux covering approximately 150 days in the interval April-August 1991 and approximately 350 days in the interval July 1992-April 1993. The source intensity in the energy range 50-300 keV is typically approx. 0.002 ph cm(exp -2)s(exp -1). We find weak evidence for variations of as much as a factor of 3 in the intensity. We derive spectral parameters of 3C273 during the intervals TJD 8422-8435 (15-28 June 1991) and TJD 8532-8546 (3-17 October 1991) for comparison with other CGRO instruments.
    Keywords: ASTRONOMY
    Type: NASA-CR-196185 , NAS 1.26:196185
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    BATSE observations of Nova Muscae 1991 (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The Compton Burst and Transient Source Experiment (BATSE) detected hard x-ray flux from Nova Muscae 1991 (GS/GRS 1124-68) during an interval of approximately 100 days beginning approximately 130 days after the January 1991 main outburst. The light curve during this secondary outburst is roughly symmetric, reaching a maximum around mid-July 1991 at an intensity of approximately 15 percent of the peak intensity during the main outburst. The hard x-ray spectrum displays a soft-to-hard evolution during the rise to maximum; the post-maximum spectral evolution is less well determined. We compare our observations with those of the GRANAT/SIGMA experiment, which covered the initial outburst well but missed most of the secondary outburst.
    Keywords: ASTRONOMY
    Type: NASA-CR-196416 , NAS 1.26:196416
    Format: application/pdf
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  • 6
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    A Maskless Gamma-Ray All-Sky Imager: BATSE/CGRO (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The non-collimated detectors of BATSE (Burst And Transient Source Experiment) on the Compton Gamma Ray Observatory (CGRO) can be used as a high sensitivity hard X-ray and low energy gamma-ray all-sky imager in the energy range between 20 keV and 2 MeV. The fluxes from sources in the sky are modulated as the spacecraft orbits the Earth. The CGRO orbital precession further allows sampling of sky in strips corresponding to the limb of the earth at any given time. The modulation data are transformed into images by various reconstruction methods. High sensitivity images of location accuracy of about 0.1 deg and source seperation of about 1 deg are obtained.
    Keywords: Astronomy
    Type: NASA-CR-204027 , NAS 1.26:204027 , IEEE Transactions on Nuclear Science (ISSN 0018-9499); 41; 4; 1313-1320
    Format: text
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