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@PHDTHESIS{Konno:622453,
      author       = {Konno, Ruslan},
      othercontributors = {Berge, David and Kowalski, Marek and Kachelriess, Michael},
      title        = {{S}earch for transient phenomena in the very-high-energy
                      gamma-ray sky with {H}.{E}.{S}.{S}.},
      school       = {Humboldt University of Berlin},
      type         = {Dissertation},
      address      = {Berlin},
      reportid     = {PUBDB-2025-00323},
      pages        = {149},
      year         = {2024},
      note         = {Dissertation, Humboldt University of Berlin, 2024},
      abstract     = {Time-domain multi-messenger astronomy is the study of
                      transient astrophysical phenomena using several messenger
                      particles and waves. The High Energy Stereoscopic System
                      (H.E.S.S.) is a ground-based telescope array, which measures
                      very-high-energy gamma rays between 30 GeV and 100 TeV.
                      Within this work, three H.E.S.S. transients follow-up
                      programs and their results are shown. At first, the nova
                      program is shown together with the detection of the 2021 RS
                      Ophiuchi (RS Oph) outburst. RS Oph is a known nova with past
                      eruptions. The analysis of the nova presented in this work
                      shows a clear detection over the first five nights of
                      observations, and a marginal detection two to four weeks
                      after the eruption. RS Oph is thus the first Galactic
                      transient phenomenon detected at ~1 TeV energies. A clear
                      variability of the spectrum is shown. A discussion of the
                      underlying physics concludes, that the observed gamma-ray
                      emission most likely stems from cooled protons accelerated
                      within an astrophysical shock. The results show
                      time-resolved particle acceleration. The second program is
                      the gravitational-waves (GWs) program. Here, the analysis of
                      four observed binary black hole merger events is shown. No
                      detection is reported, and upper limit sky maps are derived
                      instead. The viability of GW follow-up with H.E.S.S. is
                      discussed, and a case is made for a potential counterpart
                      detection. The third program is the tidal disruption event
                      (TDE) program, a pioneered program established at the
                      emergence of the source class within the last few years.
                      Unique challenges of the follow-up program are discussed,
                      and the H.E.S.S. follow-up of the event AT2019uqv is shown.
                      No detection is reported, and upper limits for AT2019uqv are
                      given instead. The interest in follow-up observations of
                      TDEs with gamma-ray instruments is stressed. In conclusion,
                      a comparison of the different programs and their
                      requirements is given, together with an outlook for the next
                      decade of ground-based gamma-ray observations.},
      cin          = {$Z_HESS$},
      cid          = {$I:(DE-H253)Z_HESS-20210408$},
      pnm          = {613 - Matter and Radiation from the Universe (POF4-613)},
      pid          = {G:(DE-HGF)POF4-613},
      experiment   = {EXP:(DE-H253)HESS-20170101},
      typ          = {PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:kobv:11-110-18452/29726-2},
      doi          = {10.3204/PUBDB-2025-00323},
      url          = {https://bib-pubdb1.desy.de/record/622453},
}