Analyses of neutrino follow-up observations of IC171106A, IC190922B, IC191001A and IC200107A measured with the MAGIC telescopes

Hendrik Bökenkamp

The origin of very high-energy cosmic rays still poses one of the big unanswered questions in astroparticle physics. Cosmic rays mainly consist of charged particles and are consequently deflected by intergalactic and interstellar magnetic fields. Thus, reconstructing the direction of their origin is challenging. Within the framework of multi-messenger astronomy, large projects such as the MAGIC telescopes and the IceCube observatory, search for correlations between different messenger particles, such as neutrinos and gamma rays, as the simultaneous production of these particles by hadronic processes is predicted in theories. In this thesis, data from follow-up observations with the MAGIC telescopes of four detected astrophysical neutrino candidates are analysed. Two different likelihood methods are used to create sky maps, which are essential for the search for associated gamma-ray point sources. One method allows the generation of spatially resolved upper limits on the gamma-ray flux. Furthermore, a new method is presented that includes the combination of data sets of slightly different pointing positions, which allows an analysis of the entire data set resulting in an increase in sensitivity of the telescopes. No significant deviation from the background-only hypothesis is observed for all analysed follow-up observations.