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HESS - Abteilung Hofmann
要旨:
γ-astronomy has opened a new window of investigation of the universe as well
as high-energy cosmic objects. In this study, several extragalactic -ray sources
were analysed within an energy range of 100 MeV and 100 TeV. Observations
were made with the H.E.S.S. experiment at TeV energies as well as the spacebased
Fermi-LAT at GeV energies. A total of 21 Active Galactic Nuclei (AGN)
were detected with H.E.S.S. and confirmed as TeV γ-ray emitters with a statistical
detection significance of more than 4σ. Nine of these sources show a
variability on daily timescales at a > 99% confidence level. A study on their
source morphology was carried out and their intrinsic extensions within the
VHE γ-ray range were estimated. The pointing accuracy of the telescopes were
determined as (25.2 ± 1.6)". Furthermore, a strong correlation between the difference
in spectral indices in the TeV and GeV energy range and their respective
redshifts was shown. Therefore, strong evidence for the influence of the EBL effect
on the TeV γ-ray spectra was found without modelling the EBL Spectrum.
Additionally, probing leptonic SSC models of emission mechanisms of γ-rays
in blazars, a luminosity relation of the form L ~ L0.93x
X between X-ray and γ–ray luminosities was empirically derived and a strong anti-correlation was found between GeV and TeV spectral indices of relatively close blazars (z ≤ 0:2) with a Pearson correlation coefficient of p = (- 0.87 ± 0.11).
Fermi-LAT data of the HBL blazars PG 1553+113 and PKS 0447-439 were
analysed in the high-energy (HE) γ-ray energy range using Pass 8 algorithms.
Accordingly, by use of the Lomb-Scargle-Periodogram and bootstrap resampling
simulations, quasi-periodicity within their respective light curves could be
verified with a significance of > 5σ. In order to explain this behaviour, instabilities
in the accretion disk-jet system, jet-precession movement and a binary
system of supermassive black holes (SMBH) were discussed. Additionally, based
on spectral and variability analyses, hints of spectral changes within the
spectral energy distribution (SED) of the radio galaxies Centaurus A and M87
were found. The origin of these spectral features could be due to the additive
HE γ-ray emission contribution of an additional second physical component.
The drive system of HESS II was optimized by introducing two monitoring
systems, which has led to a minimized risk of failure as well as an increased
observation time. A system was developed for monitoring the cooling of servo
controllers in the HESS II drive system and their respective cooling units.
An additional system was devised for the diagnosis and monitoring of critical
structural and mechanical telescope components based on a vibrational analysis.
The installation and configuration of hardware was conducted in Namibia
as well as implementation of control software for both systems in the Data-
Acquisition-System (DAQ). Eventually, preliminary vibration data was analysed
with statistical methods of time series analysis and some methods of nonlinear
dynamics.
