Bulletin of the American Physical Society
APS April Meeting 2023
Volume 68, Number 6
Minneapolis, Minnesota (Apr 15-18)
Virtual (Apr 24-26); Time Zone: Central Time
Session T14: Computational Astrophysics |
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Sponsoring Units: DAP Chair: Michael Pajkos, California Institute of Technology Room: Marquette V - 2nd Floor |
Tuesday, April 18, 2023 10:45AM - 10:57AM Author not Attending |
T14.00001: Numerical investigations of the progenitors of radio loud, long gamma-ray bursts Celia Toral, Roseanne M Cheng, Nicole M Lloyd-Ronning, Ken Luu, Lailani Kenoly We investigate a progenitor model for radio loud, long gamma-ray bursts (lGRB) where a massive star collapses in an interacting binary system with a stellar black hole companion. Using multi-code, numerical simulations, we make predictions for both the prompt and afterglow emission from these systems, through a detailed study of the jet development and its propagation into the surrounding medium. As these systems eventually evolve into binary black hole systems, our results allow us to put constraints on formation channels of gravitational wave events potentially detectable by LIGO/Virgo. In this talk, we focus on one aspect of our approach to this multi-physics, multi-scale problem in using the general relativistic hydrodynamics code Athena++ to model the post-collapse, black hole and disk central engine that leads to a lGRB. Our initial conditions of black hole spin and accretion disk mass are given by a set of numerical simulations of the binary system, prior to collapse, using Modules for Experiments in Stellar Astrophysics (MESA). In a parameter space investigation, we simulate the jet duration to place constraints on the radio afterglow emission spectra and light curves. |
Tuesday, April 18, 2023 10:57AM - 11:09AM |
T14.00002: R-process nucleosynthesis of low-mass neutron star explosions Chun Ming Yip We show that a low-mass neutron star undergoes delayed explosion after mass removal from its surface. We couple the Newtonian hydrodynamics to a nuclear reaction network of ∼ 4500 isotopes to study the nucleosynthesis and neutrino emission during the explosion. An electron anti-neutrino burst with a peak luminosity of ∼ 3 × 1050 erg s−1 is emitted while the ejecta is heated to ∼ 109 K. A robust r-process nucleosynthesis is realized in the ejecta. Lanthanides and heavy elements near the second and third r-process peaks are synthesized as end products of nucleosynthesis, suggesting that low-mass neutron star explosions could be an important source of solar chemical elements. |
Tuesday, April 18, 2023 11:09AM - 11:21AM |
T14.00003: Simulating neutron stars with flexible equation of state parametrizations in SpECTRE Isaac Legred, Yoonsoo Kim, Nils Deppe, Katerina Chatziioannou, Francois V Foucart, Lawrence E Kidder, Francois Hebert Numerical simulations of neutron star mergers are an important step in using multimessenger observations to constrain the properties of dense matter, however, such simulations are limited by the details of matter representation. We introduce a new parametrization of the dense nuclear equation of state which allows for fast, smooth approximation of hadronic models while maintaining flexibility for representing matter with phase transitions. We test the parametrization by simulating isolated neutron stars in the SpECTRE code. For low-precision modeling, we find robust fitting with little to no performance degradation relative to lower-parameter representations. At higher precision, necessary for capturing potential phase transitions, we find the new parametrization allows for evolution using arbitrary equations of state with modeling error in neutron star radii of 10 meters or less. |
Tuesday, April 18, 2023 11:21AM - 11:33AM |
T14.00004: Numerical simulations of Hall magnetohydrodynamics in neutron star crusts with Landau-quantized electrons Peter Rau, Ira Wasserman In strongly-magnetized neutron star crusts (B ≥ 1014 G), electrons are quantized into a moderate number of Landau levels. This can dramatically change the thermodynamic (specific heat capacity, magnetization, differential magnetic susceptibility) and transport properties (electrical and thermal conductivity) of the crust. In a neutron star crust, magnetic field evolution is best described using the formalism of Hall magnetohydrodynamics (MHD). We include for the first time the effects of Landau quantization on both thermodynamic and transport properties of neutron star crusts in Hall magnetothermal evolution simulations. Comparing simulations including Landau-quantization effects those excluding these effects, we assess their importance to the overall magneto-thermal history of neutron stars, in particular their impact on Ohmic heating and evolution of the magnetic field topology. |
Tuesday, April 18, 2023 11:33AM - 11:45AM |
T14.00005: Rapster: a fast code for dynamical formation of black-hole binaries Konstantinos Kritos, Vladimir Strokov, Vishal Baibhav, Emanuele Berti, Joseph Silk Gravitational wave observations revealed the existence of binary black-hole mergers with unusually asymmetric and massive components that could have formed in dense stellar environments. I present Rapster, a rapid cluster evolution code, that simulates the dynamical assembly of black-hole binaries in the cores of dense massive star clusters implementing semi-analytic prescriptions. The code is fast, and evolves a typical globular cluster within a minute. Then, I discuss applications of Rapster, such as hierarchical mergers and merger rates. |
Tuesday, April 18, 2023 11:45AM - 11:57AM |
T14.00006: The Gravitational-Wave Signature of Core-Collapse Supernovae Tianshu Wang, Adam S Burrows, David Vartanyan, Matthew S Coleman, Christopher J White The theory of core-collapse supernova (CCSN) explosions has been developed over the last six decades and is now a mature field at the interface of gravitational, particle, nuclear, statistical, and numerical physics. This theory is now buttressed by extensive numerical simulation and most 3D models now explode without artifice. The dominant gravitational-wave (GW) emission occurs during the post-shock turbulent phase in the neutrino-heated bubble bounded by the stalled (and early exploding) shock wave due to the associated violent non-radial inflow of mass plumes onto the inner proto-neutron star (PNS) core. By impinging upon the near-surface layers of the PNS, these plumes stochastically excite l=2 f-, p-, and g-modes. However, direct verification of explosion model details and the associated timelines are difficult to come by and gravitational wave signatures of this dynamical event would allow one to follow the theoretically expected sequence of events in real time. We will present in this talk state-of-the-art predictions of the signature of CCSNe as a function of progenitor mass and time. For the first time, our 3D models have captured the entire signal, not just the early phases. Features such as the excitation mechanisms, the oscillation modes, the bounce signatures, harmonic generation, and avoided crossings will be presented and discussed. Finally, we address the detectability of the emissions and features. |
Tuesday, April 18, 2023 11:57AM - 12:09PM |
T14.00007: Chaos in neutrino fast flavor instability Erick A Urquilla Orellana, Sherwood A Richers Neutrinos play a crucial role in explosive stellar events. In core collapse supernovae (CCSN), neutrinos produced thermally in the proto-neutron star drive the CCSN dynamics reviving the shock wave that causes the explosion. In neutron star mergers (NSM), neutrinos can significantly affect the ratio of neutrons to protons in the ejected mass via charged-current reactions, having a big impact on the production of heavy elements. Simulations have revealed that neutrinos undergo substantial flavor instabilities that make it challenging to fully understand the neutrino non-linear many-body dynamics. In simplified neutrino models, the presence of chaos in flavor evolution has been proposed. Since chaotic systems are very sensitive to initial conditions, i.e. trajectories of slightly different initial conditions diverge exponentially, our ability to predict the neutrino flavor behavior in CCSN and NSM could be limited. To clarify this problem, we approximate the behavior of neutrinos inside NSM by simulating neutrino flavor instabilities in a domain a few centimeters wide. Our goal is to analyze the dynamics of nearby flavor states in the presence of neutrino instabilities. We solve the neutrino quantum kinetic equation numerically including the neutrino self-interaction term in the flavor Hamiltonian, using the particle-in-cell code EMU under the mean field approximation. We conclude that nearby initial states diverge in the non-linear regime of flavor instabilities suggesting the presence of chaos. |
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