Multimessenger studies of point-sources using the IceCube neutrino telescope and the MAGIC gamma-ray telescope

Three messengers can be used to extract information about the sources of cosmic rays: photons, charged particles (cosmic rays) and neutrinos. In this work the connection between the Very High Energy (VHE) gamma-rays and neutrinos is investigated in the context of recent observations and theoretical models. In order to increase the probability of detecting a neutrino point source two new approaches were developed. First, a correlation study of possible time and directional coincidences of neutrino events, detected by the AMANDA-II telescope at the South Pole, and gamma-ray flares, observed by the Imaging Atmospheric Cherenkov Telescopes (IACTs), in the years 2004-2006, was performed for 7 objects. Second, taking the same AMANDA-II data set, 18 sources were analyzed, using a new algorithm which looks for structures in the time distribution of the neutrino events from pre-defined directions. None of the analysis resulted in a detection of a neutrino point source. The sparse time and flux state coverage of the TeV gamma-ray data is one of the most serious issues connected with any correlation study involving photons from the high energy range. This problem was addressed in this work by an analysis of historical gamma-ray data from the public archive at DESY and of the recently obtained results from the MAGIC Active Galactic Nuclei (AGN) monitoring program. Based on this data a statistical analysis of different emission states of two extragalactic VHE gamma-ray sources, Mrk 421 and Mrk 501, was performed. Due to still low flux statistics, no final conclusions concerning the probability of finding those sources in a flux state above a certain threshold can be made. The results of the MAGIC AGN monitoring program from the observational season 2007/2008 are presented here, for two sources: Mrk 501 and 1ES 1959+650. Both sources were found in a similarly low state (around 0.2 Crab) and showed moderate (Mrk 501) or no (1ES 1959+650) variability with no prominent flares. Since a part of the 2008 monitoring data of Mrk 501 was collected during a multiwavelength campaign a modeling of the broad-band Spectral Energy Distribution of Mrk 501 is also discussed.