Naslov:Extragalactic sources of rapidly variable high energy gamma radiation : Doctoral Thesis submitted to the Department of Physics, Faculty of Science, University of Zagreb for the academic degree of Doctor of Natural Sciences (Physics)
Ostali naslovi:Izvangalaktički izvori brzo promjenljivog visokoenergijskog gama zračenja
Predmet:Svemir, Gama zračenje
Datum obrane: 11.08.2008.
Format:292 str. ; 30 cm ; application/pdf
The atmosphere is an intrinsic part of any imaging atmospheric Čerenkov telescope and the telescope responseis therefore sensitive to unpredictable changes in the atmosphere. A lot of observational data takenduring non-ideal atmospheric transparency have not been analyzed because of a lack of an appropriateanalysis method that would be able to provide corrections for the imperfect transparency.On the other hand, extragalactic sources of high-energy cosmic gamma-rays (e.g. active galactic nucleiand gamma-ray bursts) are usually highly variable and the temporal characteristics of their light curvesare key to the understanding of the physics of their sources. It is therefore very important to extend theobservation time for variable sources as much as possible.In order to significantly extend the effective observational time of variable gamma-ray sources, wehave developed a new data analysis method, which first determines the actual variable atmospherictransparency from the gamma-ray measurements, and then corrects those measurements according tothe estimated atmospheric effect. To learn how the clouds influence gamma-ray measurements, we haveimplemented the simulation of clouds into the Monte Carlo simulation chain. Simulations starts withprogram Corsika, which simulates the development of particle showers in the atmosphere, and tracesthe Čerenkov light emitted by charged particles to the telescope. This method may extend the effectiveobservation time in ground-based gamma-ray astronomy in general. Here we report on the applicationof the method in the first analysis of a particularly important data set from 2001 that includes a periodof very strong activity of the blazar Mkn 421. In the near future, modern lidars will be able to preciselymeasure the distribution of the cloud density along the line of sight of the telescope, and thus providesignificantly more information for our correction method.We also developed a new approach to correlation study based on MC simulations and the Fourierconvolution. We applied the new method to analyze our CT1 data from 2003 of Mkn 421. We alsoreanalyzed correlation of some recent MAGIC data on blazars Mkn 421, Mkn 501 and newly discoveredMkn 180.
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