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  • ASTROPHYSICS  (2)
  • Space Radiation  (2)
  • 1
    Publication Date: 2013-08-31
    Description: The imaging Compton telescope (COMPTEL) is the first imaging telescope in space to explore the MeV gamma ray range. At present it is performing a complete sky survey. In later phases of the mission, selected celestial objects will be studied in more detail. Targets of special interest in the COMPTEL energy range are radio pulsars, X-ray binaries, novae, supernova remnants, molecular clouds, and the interstellar medium within the Milky Way, as well as the nuclei of active galaxies, supernovae, and the diffuse cosmic background radiation in extragalactic space. The first four months of operation demonstrated that COMPTEL basically performs as expected. The Crab is clearly seen at its proper position in the first images of the anticenter region of the Galaxy. The Crab pulsar lightcurve was measured with unprecedented accuracy. The quasar 3C273 was seen for the first time at MeV-energies. Several cosmic bursts within the COMPTEL field of view could be located to an accuracy of about 1 degree. On June 9, 11, and 15, 1991 COMPTEL observed gamma ray (continuum and line) emission from three solar flares. Neutrons were also detected from the June 9 flare. At the present state of analysis, COMPTEL achieves the prelaunch predictions of its sensitivity within a factor of 2. Based on the present performance of COMPTEL, the team is confident that COMPTEL will fulfill its primary mission of surveying and exploring the MeV sky.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center, The Compton Observatory Science Workshop; p 76-84
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  • 2
    Publication Date: 2019-06-28
    Description: Observational evidence of extended MeV emissions that may be associated with high velocity clouds (HVCs) is reported on. Based on observations acquired between 1991 and 1996 with the Compton telescope (COMPTEL), evidence is found for intense gamma ray radiation at 0.75 to 3 MeV from the general direction of two HVC regions. One bright gamma ray excess is located between the HVC complexes M and A, adjacent to the Lockman hole and is seen to approximately cover a sky area of exceptionally low H I column densities. A second source is detected at the high velocity end of complex C near the Draco Nebula. Both gamma ray excesses appear to consist of a time variable source and a diffuse emission component. The enhanced diffuse soft X-rays seen by Rosat from both HVC regions may be closely related to the gamma ray emission in terms of bremsstrahlung arising from HVC interactions with the galactic disk or lower halo.
    Keywords: Space Radiation
    Type: Proceedings of 2nd INTEGRAL Workshop 'The Transparent Universe'; 119-122; ESA-SP-382
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  • 3
    Publication Date: 2019-07-18
    Description: The spectrometer on INTEGRAL (SPI) is a coded-aperture gamma-ray telescope with moderate angular resolution (3 deg) and superior energy resolution (2 keV at 511 kev). One of it's principal science goals is the detailed study of 511 keV electron-positron annihilation from our Galaxy. The origin of this radiation remains a mystery, however current morphological studies suggest an older stellar population. There has also been recent speculation on the possibility of the existence of light (〈 100 MeV) dark matter particles whose annihilation or decay could produce the observed 511 keV emission. In this paper we summarize the current results from SPI, compare them with previous results and discuss their implication on possible models for the production of the annihilation radiation.
    Keywords: Space Radiation
    Type: AAS Meeting; Jan 01, 2005; San Diego, CA; United States
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  • 4
    Publication Date: 2019-07-13
    Description: The imaging Compton telescope COMPTEL on board the Compton Gamma-Ray Observatory (CGRO) measures gamma-rays in the energy range 0.75-30 MeV with an energy resolution of 9.7% full width at half maximum (FWHM) at 1 MeV. From June 15 to 28, 1991 and again from October 3 to 17, 1991 the region containing the supernova SN 1991T was observed. A search for gamma-ray line emission from the supernova yields no detection of line emission from the supernova. 2 sigma upper limits for the two predicted lines at 847 keV and at 1.238 MeV of approximately equal to 3 x 10(exp -5) photons/(sq cm)(s) were derived. These limits are compared with the predictions of some theoretical models and constraints imposed by these limits on these models are discussed.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 292; 2; p. 569-579
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