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Hsu, Ching-Cheng (2010): Long Term Monitoring of Mrk421 from 2005-2008 with the MAGIC telescope. Dissertation, LMU München: Faculty of Physics
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Abstract

Active Galactic Nuclei (AGNs) are among the most luminous objects in the universe. At the center of an AGN, there is a SuperMassive Black Hole (SMBH) with a mass above million Solar mass, which is believed to be the engine of a huge energy output. Blazars are a subclass of AGNs, which usually have bipolar jets, one of which is pointing towards us. Markarian 421 (Mrk421) is one of the bright and nearby established TeV blazars. Its TeV emission was first discovered by the Whipple telescope in 1992 and it became one of the most studied extra-galactic objects in the TeV regime. Mrk421 shows strong variabilities in time and amplitude in different energy regimes. The Mrk421 data collected so far from many historic multiwavelength observations is not yet sufficient to fully constrain the theoretical models. In particular, it is not yet clear whether the leptonic or hadronic processes play a decisive role inside the jets. Due to short duty cycles and limited observation time, studies of bright TeV (E > 100 GeV) blazars are mostly restricted to flaring episodes or short time period (a few days to weeks) of multiwavelength campaigns. However, to study these objects long time monitoring is needed in order to constrain theoretical jet models. Only unbiased long-term studies are adequate for the determination of flaring states probabilities and for estimating the statistical significance of possible correlations between TeV flaring states and other observables, like X-ray or neutrinos. Besides, regular observations can also provide triggers for multiwavelength ToO observations. This is particularly necessary for identifying and studying orphan TeV flares. MAGIC has observed Mrk421 since 2004 and then constantly monitored this source from 2006. In this thesis, the Mrk421 data taken from 2005 to 2008 will be presented. The physics results from several times of joint observations will be also discussed. To further increase the sensitivity of the MAGIC telescope, a second telescope was built. The photosensors, PMTs, with light collectors, Winston Cones, of the second telescope were tested in order to know the performance of the new system. The different characteristics of the PMTs and their performance tests will be also described.