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  • Other Sources  (6)
  • 1990-1994  (6)
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  • 1
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    Spectral determinations for discrete sources with EGRET (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The ability of the EGRET (Energetic Gamma-Ray Experimental Telescope) to determine the spectral parameters of point sources in 14-day exposures, as planned for the initial survey phase of the GRO (Gamma Ray Observatory) mission, is explored by numerical simulation. Results are given for both galactic and extragalactic objects as a function of source strength and for representative levels of diffuse background emission.
    Keywords: ASTRONOMY
    Type: NASA, Goddard Space Flight Center, The Energetic Gamma-Ray Experiment Telescope (EGRET) Science Symposium; p 201-213
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Observation of high-energy gamma rays from the quasi-stellar object CTA 102 (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The quasar CTA 102 (QSO 2230 + 114) was observed four times in 1991-1992 by the EGRET high-energy gamma-ray telescope on the Compton GRO satellite. In the 1992 January 23-February 6 observation, emission was detected at the level (2.4 +/- 0.5) x 10 exp 7 photons/sq cm s (E is greater than 100 MeV). The other observations produced upper limits or detections with lower significance which are consistent with the same flux. The photon spectrum can be represented by a power law with a number index of 2.6 +/- 0.2, the softest so far observed by EGRET. The emitted gamma-ray luminosity, if isotropic, is 5 x 10 exp 47 ergs/s (H(0) = 75 km/s Mpc , q(0) = 0.5), although there are good reasons to believe that the gamma emission is strongly beamed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 414; 1; p. 82-85.
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Observations of the Crab pulsar and nebula by the EGRET telescope on the Compton Gamma-Ray Observatory (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Crab pulsar and nebula were observed three times in 1991 April to June by the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma-Ray Observatory (CGRO): April 23 to May 7, May 16 to 30, and June 8 to 15. The results of analysis of the gamma-ray emission in the energy range from 50 MeV to more than 10 GeV are reported. The observed gamma-ray light curve exhibits two peaks separated in phase by 0.40 +/- 0.02, consistent with previous observations. The total pulsed emission from the Crab pulsar is found to be well represented by a power-law spectrum, softer than the spectrum measured by COS B (Clear et al., 1987). The interpulse emission has a harder spectrum than either of the pulses. The evidence for pulsed emission above 5 GeV in the EGRET data is not conclusive. Unpulsed emission in the energy range 50 MeV to 5 GeV was detected, with an indication of a hardening of the unpulsed spectrum above about 1 GeV. There was a significant change in the light curve over the 2 months of these observations, although the shape of the spectrum remained constant.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 409; 2; p. 697-704.
    Format: text
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  • 4
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    Performance of the EGRET astronomical gamma ray telescope (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: On April 5, 1991, the Space Shuttle Atlantis carried the Compton Gamma Ray Observatory (CGRO) into orbit, deploying the satellite on April 7. The EGRET instrument was activated on April 15, and the first month of operations was devoted to verification of the instrument performance. Measurements made during that month and in the subsequent sky survey phase have verified that the instrument time resolution, angular resolution, and gamma ray detection efficiency are all within nominal limits.
    Keywords: ASTRONOMY
    Type: IEEE Transactions on Nuclear Science (ISSN 0018-9499); 39; 4; p. 993-996.
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  • 5
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    Plastic scintillator block as photon beam monitor for EGRET calibration (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The EGRET (Energetic Gamma Ray Experiment Telescope) detector has been calibrated at SLAC (Stanford Linear Accelerator) and, to a lesser degree, at the MIT Bates Linear Accelerator Center. To monitor the photon beams for the calibration, a plastic scintillator block, 5 cm x 5 cm in cross section, 15 cm in length, and viewed by a single photomultiplier tube, was used for the entire beam energy range of 15 MeV to 10 GeV. The design operation, and method of analysis of the beam intensity are presented. A mathematical framework has been developed to treat the general case of a beam with multiphoton beam pulses and with a background component. A procedure to deal with the fluctuations of the beam intensity over a data-taking period was also developed. The photon beam monitor is physically sturdy, electronically steady, simple to construct, and easy to operate. Its major merits lie in its sheer simplicity of construction and operation and in the wide energy range it can cover.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: IEEE Transactions on Nuclear Science (ISSN 0018-9499); 38; 597-605
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  • 6
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    The estimation of background production by cosmic rays in high-energy gamma ray telescopes (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: A calculational method of estimating instrumental background in high-energy gamma-ray telescopes, using the hadronic Monte Carlo code FLUKA87, is presented. The method is applied to the SAS-2 and EGRET telescope designs and is also used to explore the level of background to be expected for alternative configurations of the proposed GRITS telescope, which adapts the external fuel tank of a Space Shuttle as a gamma-ray telescope with a very large collecting area. The background produced in proton-beam tests of EGRET is much less than the predicted level. This discrepancy appears to be due to the FLUKA87 inability to transport evaporation nucleons. It is predicted that the background in EGRET will be no more than 4-10 percent of the extragalactic diffuse gamma radiation.
    Keywords: SPACE RADIATION
    Type: IEEE Transactions on Nuclear Science (ISSN 0018-9499); 38; 553-558
    Format: text
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