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@PHDTHESIS{Korntreff:155630,
      author       = {Korntreff, Christina},
      title        = {{N}umerical simulation of gas-induced orbital decay of
                      binary systems in young clusters},
      volume       = {25},
      school       = {Universität Köln},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2014-04688},
      isbn         = {978-3-89336-979-9},
      series       = {Schriften des Forschungszentrums Jülich. IAS Series},
      pages        = {98 S.},
      year         = {2014},
      note         = {Universität Köln, Diss., 2014},
      abstract     = {A large fraction of stars (≈ $50\%$ of the field
                      population) are not single but part of a binary or multiple
                      system. These binary systems form from the gas and dust in
                      molecular clouds largely building clusters that are
                      initially still embedded in the star-forming gas. Here the
                      question arises whether the properties and frequency of
                      binaries change during this gas-embedded phase. It is known
                      that the gravitational interactions between stars in a
                      cluster environment can destroy long-period binaries (>
                      10$^{5}$ days). However, not only can the interaction
                      between the stars themselves change the binary properties
                      but also those between binary systems and the surrounding
                      gas. There, the binary potential torques the nearby gas,
                      producing an outgoing acoustic wave. This wave transports
                      angular momentum from the binary to the gas, resulting in a
                      decay of the binary orbit. This effect is the central focus
                      of the thesis presented here. First, an analytic
                      approximation for the gas-induces orbital decay by Stahler
                      (2010) was applied to a binary population and the results
                      compared to observations. It was found that the process of
                      orbital decay significantly changes the properties of short
                      period binaries (< 10$^{5}$ days). The resulting period
                      distribution resembles the one observed for solar-mass
                      stars, but fails to do so for other mass ranges. The
                      analytic approximation treats only the effect on binary
                      systems with circular orbits and the wave generation is not
                      calculated explicitly. Since, most binary systems have
                      eccentric orbits, a 3D hydrodynamic simulation was developed
                      to avoid these restrictions. It calculates the gravitational
                      binary - gas interaction, the wave generation, and the
                      resulting orbital decay. An extensive parameter study was
                      performed to investigate the dependency of the orbital decay
                      on the binary and gas properties. It was found that the gas
                      density, embedded time span and mass-ratio show a similar
                      scaling as predicted by the analytic approximation. By
                      contrast, all binary and gas properties which influence the
                      wave generation show different dependencies. In particular,
                      it is shown that eccentric orbits lead to a faster orbital
                      decay than their circular counterparts. Eventually, all
                      these effects were combined in a fit formula. Applying this
                      fit-formula to a binary population, the resulting period
                      distribution shows a better matching mass dependency, but
                      still does not resemble the observed period distributions.
                      The cluster model chosen here is only one example and it is
                      still unknown which cluster types contribute to the field
                      population. Furthermore, future observations of young binary
                      systems and their environment could restrict the parameter
                      space presented here. Having detailed knowledge of the
                      binary’s environment, the method developed in this thesis
                      can be used to deduce what impact the gas-induced orbital
                      decay has on a binary population.},
      keywords     = {Dissertation (GND)},
      cin          = {JSC},
      cid          = {I:(DE-Juel1)JSC-20090406},
      pnm          = {411 - Computational Science and Mathematical Methods
                      (POF2-411)},
      pid          = {G:(DE-HGF)POF2-411},
      typ          = {PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:0001-2014072202},
      url          = {https://juser.fz-juelich.de/record/155630},
}