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Bartko, Hendrik (2007): Observation of Galactic Sources of Very High Energy Gamma-Rays with the MAGIC Telescope. Dissertation, LMU München: Faculty of Physics
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Abstract

One of the most important 'messengers' of many high energy phenomena in our universe are gamma-rays. The detection of very high energy (VHE) cosmic gamma-radiation by ground-based Cherenkov telescopes has opened a new window to the Universe, called gamma-ray astronomy. It is a rapidly expanding field with a wealth of new results, particularly during the last two years, due to the high sensitivity of a new generation of instruments. The major scientific objective of gamma-ray astronomy is the understanding of the production, acceleration and reaction mechanisms of very high energy particles in astronomical objects. This is tightly linked to the search for sources of the cosmic rays. The MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) telescope is one of the new generation of Imaging Air Cherenkov Telescopes (IACT) for VHE gamma-ray astronomy. With its 17 m diameter mirror the MAGIC telescope is today the largest operating single-dish IACT. It is located on the Canary Island La Palma (28.8 deg. N, $17.8 deg. W, 2200 m asl.). Recently, eight new galactic VHE gamma-ray sources were detected by the HESS collaboration. They have either no or very weak counter-parts in other wavelengths. This makes them ideal candidates for accelerators of hadronic cosmic rays. The Galactic Center was also found to be a source of VHE gamma-rays by various groups. However, the reported spectra differed significantly such that the nature of the source could not yet be identified.In this thesis, observations of three galactic sources of VHE gamma-rays with the MAGIC telescope are discussed: the source at the Galactic Center and two sources in the galactic disc HESS J1813-178 and HESS J1834-087. The positions, extensions, morphologies and the differential fluxes of these sources are presented using the data from the MAGIC telescope, and possible flux variations with time are studied. To identify the gamma-ray production mechanism and the nature of the sources, the gamma-ray sources are related to possible counter-parts in other wavelength bands. For HESS J1813-178, leptonic and hadronic models for the multiwavelength emission are developed and compared to the data to identify the physical processes at work in the source. The source at the Galactic Center is shown to be a stable emitter of VHE gamma-rays, and the implications for the source models are discussed. As these sources are located in the southern sky and can only be observed under large zenith angles with the MAGIC telescope, suitable observation and analysis procedures for large zenith angles had to be developed. In order to achieve the best possible background determination, the sources were observed in the off-source tracking observation mode. To further increase the sensitivity of the MAGIC telescope, new ultra-fast read-out electronics components have been developed as an upgrade project for the MAGIC telescope. The performance of the new system is evaluated based on prototype tests in the MAGIC telescope at La Palma. The production, tests, and installation on the MAGIC telescope of a full-scale read-out system are described.