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The energy spectrum of very high energy gamma rays from the Crab Nebula as measured by the H.E.S.S. array

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Abstract (Summary)
The goal of this thesis is to implement the methods developed for the HEGRA experiment to reconstruct the geometry and energy of the airshowers induced by the cosmic high-energy gamma rays into the software environment of the H.E.S.S. experiment. Furthermore, using the implemented algorithms, a search for the unpulsed emission is aimed in the energy range between 300 GeV and 20 TeV from the Crab Nebula using the first stereoscopic data taken during October and November 2003 with the 3 telescope configuration of the H.E.S.S. array in Phase-I. The Phase-I of the H.E.S.S. array was completed in December 2003 by the addition of the fourth telescope. By testing the reconstruction algorithms of a complete Phase-I H.E.S.S. array with Monte Carlo simulations, it is found that the resolution of the reconstructed direction and energy of a ?-ray event from a zenith angle of 45? is around 0.15? and 14%, respectively. The data on the Crab Nebula including runs with wobble offset of ±0.5? and ±1.0? is collected at zenith angles from 45? to 50? for a total of 4 hours and gives a background subtracted signal of about 50 standard deviations. The differential energy spectrum of the unpulsed ?-ray emission from the Crab Nebula is found to be d?/dE = (3.37 ± 0.47) × 10?11 E?2.59±0.12 cm?2 s?1TeV?1 between 450 GeV and 20 TeV after all cuts. The integral flux above 1 TeV is (2.11 ± 0.29) × 10?11cm?2s?1. These results are consistent with the results published by other experiments, in particular HEGRA and Whipple. The results agree well with the expectation from synchrotron self-Compton models for TeV emission range. The magnetic field in the region, where TeV ? rays are produced, is found to be 0.18±0.01 mG. This result agrees with the magnetic field values deduced by the models. The results obtained for the Crab Nebula in this thesis demonstrate the performance of the H.E.S.S. array.
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School:Oberlin College

School Location:USA - Ohio

Source Type:Master's Thesis

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