Long-term observations of the TeV blazar 1ES1959+650

Abstract

Throughout this thesis, the spectral and temporal long-term behavior of the Active Galactic Nucleus (AGN) 1ES1959+650 is studied. Being a blazar, i.e. an AGN with a highly relativistic plasma outflow pointing towards the Earth, and having shown strong hints of hadronic emission processes in the past, 1ES1959+650 is a primary candidate for a source of cosmic rays. The origin of these ultra high energetic charged particles is the central question of astroparticle physics. Therefore, 1ES1959+650 has been monitored with the MAGIC telescope since 2004, measuring very high energy (VHE) gamma-rays. The resulting time-integrated energy spectrum reported here is by far the most exact one determined for this source up to now. Also the temporal variability for different wavelength bands, which should be connected in the case of most non-hadronic emission processes, is examined in this thesis. While strong variations occur in the optical and X-rays, the VHE gamma-ray emission is compatible with a constant flux. Furthermore, the time-integrated spectral energy distribution is compiled from radio to VHE gamma-rays and modeled for hadronic and leptonic emission scenarios to unveil the character of the emitting particles. Unexpected results are obtained on the spectral shape of the observed blazar, especially in high energy gamma-rays. By this, 1ES1959+650 is one of the very first high frequency peaked blazars whose non-thermal emission cannot be explained with a single-zone SSC model. Additionally, in this thesis the idea of long-term monitoring of blazars at VHE gamma-rays is pursued further. The FACT telescope, the first application of G-APDs as photosensors in an imaging atmospheric Cherenkov telescope, has recently been constructed and already during its commissioning phase reported on very promising first results. After the commissioning, it will be devoted to monitoring observations of bright blazars. For the construction of this telescope, the completely reworked aluminum mirrors have been characterized, including measurements of the focal lengths and the spot sizes of a reflected point-like light source. Finally, it is presented that DWARF, a global network of a small number of Cherenkov telescopes dedicated to monitoring observations of TeV-bright blazars, will be well suited to obtain comprehensive, well sampled lightcurves which are needed to study possible temporal correlations between VHE gamma-rays and other wavelengths.