Outflows, Mergers, and Tori, Oh My!

• Author / Creator

  Steven Fahlman

• We study long-term evolution of accretion tori around hypermassive neutron stars in the context of neutron star merger transients, their involvement in the creation of short gamma-ray bursts, and their role in the synthesis of the heaviest elements in the universe. First we conduct 2D axisymmetric hydrodynamic simulations with selected initial conditions relevant to the neutron star merger GW170817, and compare our ejected masses and velocities to those inferred from standard two-component kilonova modeling of the event. Our suite of microphysics includes neutrino transport, nuclear recombination, and a viscous parameterization of magnetic stresses. We find that these are not sufficient to drive the ejected blue mass of the kilonova to velocities of 0.3c required by standard kilonovae fits, motivating the need for including full 3D magnetohydrodynamics in simulations. As an initial step to implementing this, we modify the unsplit solver in the FLASH code to evolve hydrodynamics in 3D spherical coordinates. Tests of the code are demonstrated via the initialization and evolution of a Sedov blast wave and a 3D equilibrium torus.

• Subjects / Keywords

  • Kilonova
  • Hypermassive Neutron Star
  • Torus Outflows
  • Neutron Star merger

• Graduation date

  Fall 2019

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-6877-8m55

• License

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