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Institut für Astronomie und Astrophysik

Abteilung Astronomie

Sand 1, D-72076 Tübingen, Germany
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Dissertation Daniel Gottschall

The Mirror Alignment and Control System of H.E.S.S. Phase II, and Observational Studies of TeV Shell Candidates and of the Nova Sgr 2015 No. 2 with H.E.S.S.

The High Energy Stereoscopic System (H.E.S.S.) is a hybrid system of five Imaging Atmospheric Cherenkov Telescopes of two different types designed to detect very high energy gamma-rays with energies from tens of GeV to tens of TeV. One key component of the telescopes are the reflective dishes with mirror areas of 614m2 for the large size telescope CT5 and 108m2 for the medium size telescopes CT1-4 consisting of a large number of mirror segments. The first part of these thesis deals with the alignment of the telescopes. The initial alignment of the larger telescope CT5 has been studied in this work, resolving a problem with the monitoring of the quality of the alignment. After improving the system, a new alignment was done and the possibility of using a fast re-pointing for transient sources from a mirror alignment perspective was investigated and successfully commissioned. Continuous support for the alignment system was provided, including a long-term monitoring system of the stability of the alignment and a new alignment of CT3 after a mirror exchange. The second part of the thesis covers a study of new supernova remnants (SNRs) discovered at TeV energies. The large field of view of H.E.S.S. is well suited for survey observations and very extended sources. Based on the H.E.S.S. Galactic plane survey (HGPS), for the first time, very high energy (VHE) gamma-ray sources were selected as supernova remnant (SNR) candidates solely based on VHE gamma-ray observations. The three SNR candidates HESS J1534-571, HESS J1614-518 and HESS J1912+101 were studied in detail including available multi-wavelength information. HESSJ1534-571 was associated with a SNR candidate in the radio band and therefore classified as SNR. Possible emission scenarios were investigated even though the results remain inconclusive for the time being. The thesis has been concluded with a study of the nova V5668 Sgr at TeV energies. The discovery of emission from classical novae in the GeV band with the Large Area Telescope on the Fermi Gamma Ray Space Telescope Spacecraft (Fermi-LAT) triggered an increased activity of H.E.S.S. to observe bright or in the GeV band detected novae. The nova V 5668 Sgr was the first nova observed with the newer telescope CT5 optimized for low energy observations. The source was not detected with H.E.S.S., but based on the detection with Fermi-LAT and the upper limits derived from the H.E.S.S. data, the hadronic component of an emission model was constraint.
Key words: Astronomy, Gamma-ray astronomy, Mirror alignment, H.E.S.S. telescopes, supernova remnant, nova

Online-Publikation: http://hdl.handle.net/10900/83449

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