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@PHDTHESIS{Skole:316967,
      author       = {Skole, Christian},
      title        = {{S}earch for extremely short transientgamma-ray sources
                      with the {VERITAS} observatory},
      school       = {Humboldt-Universität zu Berlin},
      type         = {Dr.},
      reportid     = {PUBDB-2017-00337},
      pages        = {165 p.},
      year         = {2016},
      note         = {Humboldt-Universität zu Berlin, Diss., 2016},
      abstract     = {In astronomy, many of the observed sources show a transient
                      behavior. Examples aregamma-ray bursts (GRBs) and active
                      galactic nuclei (AGN). For those source typesthe variability
                      can be very short, in the order of seconds to minutes.
                      Measuringthe flux variations is necessary to understand the
                      underlying physical processesresponsible for the emission.
                      However, the detection of very short flares can bedifficult
                      in the very high-energy range, in which imaging atmospheric
                      Cherenkovtelescopes like VERITAS are operating. This is due
                      to the large background andthe comparable low signal
                      rates.This thesis discusses the implementation of advanced
                      statistical methods (exp-test and Bayesian-Blocks) into the
                      VERITAS analysis framework, that are optimized forthe
                      detection of significant variations in the event rate. The
                      performance of thesemethods is evaluated and compared by
                      using Monte Carlo simulations of minute-scale flares for two
                      different VERITAS states, pre- and post-hardware-upgrade.
                      Itis shown that the advanced methods can improve the
                      detection sensitivity for shortflares with high fluxes of
                      more than the Crab flux (Crab unit = C.U.). For
                      example,flares at 2 C.U. with short durations down to 100
                      sec are now detectable, which isnot possible with the
                      standard method. In the next step of this thesis, 6 GRB
                      afterglows and 450 runs of AGN data, observedby VERITAS, are
                      analyzed with the advanced methods. In none of the AGN runsa
                      significant detection of short time variability is made,
                      which is in consistence withthe canonical AGN models. The
                      investigation of the 6 GRB afterglows also didnot reveal any
                      short flares in the GeV-TeV range. However, for two of them
                      it waspossible to estimate an upper flux limit of 1.25 C.U.
                      (≈3,7·10$^{−10}$ erg cm$^{−1}$s$^{−1}$[0,1;10
                      TeV]).},
      cin          = {ZEU-EXP/AT / ZEU-CTA},
      cid          = {$I:(DE-H253)ZEU-EXP_AT-20120731$ /
                      I:(DE-H253)ZEU-CTA-20120731},
      pnm          = {613 - Matter and Radiation from the Universe (POF3-613)},
      pid          = {G:(DE-HGF)POF3-613},
      experiment   = {EXP:(DE-H253)VERITAS-20170101},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.3204/PUBDB-2017-00337},
      url          = {https://bib-pubdb1.desy.de/record/316967},
}