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  • Springer  (10)
  • American Geophysical Union  (8)
  • Nature Publishing Group  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 257 (1975), S. 375-376 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Results of a balloon flight with our double Compton telescope3'4 now set an upper limit to the soft y-ray flux between 1.5 and 10 MeV from the Crab Nebula which is in severe contradiction to the flux values published previously1'2 and rules out the existence of an excess-at least of this magnitude. ...
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 274 (1978), S. 344-346 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Diffuse cosmic X- and y-radiation has been observed during the past decade after much experimental effort by many groups. The existence of this radiation in the X-ray range has been established for several years. Below 100 keV, the radiation is isotropic to within 4% in angular intervals of 10 ...
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract COMPTEL on board CGRO has observed a very strong (S[〉 0.3 MeV] = 2.03 × 10−4 erg cm−2), complex, and long lasting (162 s) gamma-ray burst on February 17, 1994 (GRB 940217). Temporal fluctuations occur on timescales as short as 100 ms. Hard-to-soft spectral evolution has been observed during the burst emission and also within individual peaks. The photon spectra obtained within the 6 peaks can be modelled by single power law spectra and by broken power laws with break energies at around 1 MeV. The best-fit power law slopes vary between 1.1 and 3.5 throughout the event. The burst is located at [α 2000,δ 2000] = [29.5°, 3.8°] with a 3σ error radius of 0.9°. COMPTEL does not detect any significant “post-burst” emission (as reported by EGRET) at low energies (〈 30 MeV), and our upper limits are marginally consistent with the EGRET detections. Using high energy spectral and temporal information, distance limits to GRB 940217 have been derived.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1572-946X
    Keywords: gamma-ray bursts: observations ; locations ; spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In its first three years of operation, the COMPTEL instrument on theCompton Gamma-Ray Observatory has measured the locations (mean accuracy ∼1°) and spectra (0.75-30 MeV) of 18 gamma-ray bursts and continues to observe new events at a rate of ∼1/month. With good angular resolution and sensitivity at MeV energies, the growing COMPTEL burst catalog is an important new piece of evidence in the on-going GRB mystery. The COMPTEL burst locations are consistent with an isotropic distribution of sources, yet the spatial coincidence of two of the bursts indicates the possibility of repetition. The COMPTEL burst spectra are in most cases consistent with a single power law model with spectral index in the range 2–3. However, two bursts show evidence of a spectral break in the MeV range. Measurement of rapid variability at MeV energies in the stronger bursts provides evidence that either the sources are nearby (within the Galaxy) or the gamma-ray emission is relativistically beamed. We present an overview of analysis results obtained from the COMPTEL burst catalog concentrating on the search for burst repetition and the implications of highly variable MeV emission.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 61 (1974), S. 250-256 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 69 (1982), S. 212-219 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Notes: Abstract During the last decade the exploration of the sky in the light of gamma rays has begun by means of satellite- and balloon-borne instruments. Like in other ranges of the electromagnetic spectrum the Milky Way clearly stands out against the rest of the sphere. Part of the galactic γ-ray emission is due to discrete sources, part is diffuse in origin and is produced in interstellar space. Some of the discrete γ-ray sources are radio pulsars, the nature of the other sources is still unknown. The intensity distribution of the diffuse galactic γ-ray component is consistent with a decrease of the cosmic-ray intensity towards the outer part of the galaxy. The identification of the cosmic-ray sources will be one of the main objectives of the next generation of γ-ray telescopes.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 323 (1986), S. 692-694 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The radioactive isotope 26A1 has a half-life of 7.4xl05yr, decaying into an excited state of 26Mg 82% of the time by emission of a positron and 18% of the time by electron capture. 26Mg decays to its ground state 99.7% of the time by emission of a 1.81-MeV ?-ray. There is, therefore, a relationship ...
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 30 (1974), S. L17 
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A Monte Carlo program has been developed in order to examine the influence of multiple Compton scattering in the atmosphere on the spectrum of cosmic diffuse gamma rays. It is shown that the corrections to the made to the measurements of the double-Compton gamma telescope at 2·5 gr cm−2 rest atmosphere by Schönfelder and Lichti (1974) are lower than 4% in the energy range between 1.5 and 10 MeV.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 72 (1985), S. 133-138 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Space science reviews 36 (1983), S. 249-266 
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Recently the galactic plane has been observed in the low and medium energy gamma-ray range in the directions towards the center and anticenter. Spectral measurements are now available at those energies, where the contribution from π°-decay gamma rays can be neglected. The high MeV-fluxes observed in both parts of the Galaxy are an indication of either a strong electron induced component or a high contribution from unresolved sources. Several interstellar cosmic-ray electron spectra have been used to calculate the contribution from electron bremsstrahlung and inverse Compton collisions with optical, infrared and 2.7 K black-body photons. From these calculations restrictions on the interstellar electron spectrum are derived.
    Type of Medium: Electronic Resource
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