Computer Science
Scientific paper
May 1971
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1971saosr.334.....g&link_type=abstract
SAO Special Report #334 (1971)
Computer Science
9
Scientific paper
Calculations for the Compton-synchrotron spectrum of gamma-rays produced in the Crab nebula have been performed using the exact Comption scattering formalism, an assumed radial variation (1/r) of the nebular magnetic field due to the pulsar and the measured radial variation of the optical intensity. A relatively higher yield of gamma-rays near ~ 1012 eV was found than in previous calculations assuming homogeneity. In an effort to detect such gamma-rays by the detection of the extenive air showers (EAS) they would contribute to the background of cosmic ray-initiated showers, previous EAS studies have been reviewed to determine the possibility of identification of the primary particle initiating an individual EAS. The muon component and longitudinal development were found to be most important. Numerous experimental observations of EAS were then conducted to ascertain whether these effects could be observable in the detailed structure of the Čerenkov light produced in EAS. Strong evidence is presented for the existence of a unique component of the Čerenkov radiation from the penetrating shower cores, tentatively identified as the muon component. A three dimensional Monte Carlo calculation of EAS initiated by protons confirmed this hypothesis. The experimental methods for identifying the core Čerenkov emission were then applied to observations of EAS from the direction of the Crab nebula. Those EAS not detected at the penetrating core were regarded, in accordance with the calculations, as candidate gamma-ray events. A ~ 2 σ increase in these events was observed within 2 minutes of the transit of the Crab nebula through the detector array field of view. From this a new upper limit is estimated for the detection (>3σ) of continuous gamma rays with Eγ > 6 X 1011 eV to be F(>Eγ) < 3.5 X 10-11 photons/cm2-sec, and a limiting nebular magnetic field is also given. From all the data recorded with timing information a possible detection is reported at the > 4σ level of pulsed gamma-rays with Eγ > 6 X 1011 eV in the interpulse of NP-0532. The flux would be F(>Eγ) ~ 1.65 X 10-11 photons/cm2-sec and appears consistent with an extrapolation of the x-ray pulse spectrum though it contradicts previous upper limits at Eγ > 2 X 1011 eV. Finally, the EAS identification methods were applied to a study of the relative strength of the cores in some 300 EAS. From calculations of EAS initiated by He and C nuclei as well as protons, the cosmic ray composition at 3 X 1012 eV is inferred to be in approximate agreement with direct measurements at <~ 1011 eV except for a suggestion of an over abundance of superheavy cosmic rays.
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