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Abstract:
Gamma-ray bursts (GRBs) and supernovae (SNe) are well known examples of celestial
transient events. Their tremendous energy release provides the ability to accelerate
particles to the highest energies. The High Energy Stereoscopic System (H.E.S.S.) is an
array of four imaging atmospheric Cherenkov telescopes, covering gamma-ray energies
between 100 GeV and 100TeV (VHE range). In this work the H.E.S.S. data on GRBs are
searched for VHE gamma-ray emission. Amongst them is the analysis of GRB 100621A,
the brightest X-ray source so far detected by the Swift satellite. Measurements at lower
energies make it a promising candidate within the sensitivity reach of the H.E.S.S. instrument,
however no indication of VHE emission is found. The derived upper limits
constrain the existence of additional spectral components and provide important input
for understanding the emission process. Furthermore, H.E.S.S. pointing positions are
compared to a recently created, unified SN catalogue in order to identify extragalactic
SNe accidentally in the field of view during the observation of other targets. The analysis
reveals no significant detection, which allows one to constrain possible VHE emission scenarios.
This work also includes a technical discussion of the H.E.S.S. telescope pointing
accuracy. A new approach, the SingleCCD concept, is discussed and evaluated, which is
interesting for the next generation of imaging atmospheric Cherenkov telescopes.
