Bulletin of the American Physical Society
APS April Meeting 2014
Volume 59, Number 5
Saturday–Tuesday, April 5–8, 2014; Savannah, Georgia
Session X8: Supernovae and Gamma Ray Bursts I |
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Sponsoring Units: DAP Chair: Ignacio Taboada, Georgia Institute of Technology Room: 202 |
Tuesday, April 8, 2014 10:45AM - 10:57AM |
X8.00001: Models of Core-Collapse Supernova Explosions and Uncertainties in Presupernova Stellar Structure Christian D. Ott, Sean M. Couch Stars are not perfectly spherical. There are strong indications from the first set of multi-dimensional simulations of the late stages of stellar evolution that precollapse stellar structure may harbor large scale deviations from spherical symmetry. We discuss current uncertainties in presupernova stellar structure and show results from a numerical experiment that demonstrates that asphericities caused by vigorous convective Si/O shell burning can have a pivotal effect on supernova dynamics. [Preview Abstract] |
Tuesday, April 8, 2014 10:57AM - 11:09AM |
X8.00002: Simulating Radiation Transport in Curved Spacetimes Eirik Endeve, Cory Hauck, Yulong Xing, Christian Cardall, Anthony Mezzacappa We are developing methods for simulation of radiation transport in systems governed by strong gravity (e.g., neutrino transport in core-collapse supernovae). By employing conservative formulations of the general relativistic Boltzmann equation\footnote{Cardall, C.Y., Endeve, E., \& Mezzacappa 2013, Phys. Rev. D {\bf 88}, 023011}, we aim to develop methods that are (i) high-order accurate for computational efficiency; (ii) robust in the sense that the phase space density $f$ preserves the maximum principle of the physical model ($f\in[0,1]$ for fermions); and (iii) applicable to curvilinear coordinate systems to accommodate curved spacetimes, which result in gravity-induced frequency shift and angular aberration. Our approach is based on the Runge-Kutta discontinuous Galerkin method\footnote{Cockburn \& Shu 2001, J. Sci. Comput. {\bf 16}, 173-261}, which has many attractive properties, including high-order accuracy on a compact stencil. We present the physical model, describe our numerical methods, and show results from implementations in spherical and axial symmetry. Our tests show that the method is high-order accurate and strictly preserves the maximum principle on $f$. We also demonstrate the ability of our method to accurately include effects of a strong gravitational field. [Preview Abstract] |
Tuesday, April 8, 2014 11:09AM - 11:21AM |
X8.00003: Three-dimensional simulation of core-collapse supernovae with CHIMERA O.E.B. Messer, Eric J. Lentz, Stephen W. Bruenn, J.A. Harris, W. Raphael Hix, Anthony Mezzacappa, John M. Blondin, Eirik Endeve, Pedro Marronetti, Konstantin Yakunin Core-collapse supernovae are driven by a multidimensional neutrino radiation hydrodynamic (RHD) engine, and full simulation ultimately requires symmetry-free three-dimensional (3D) RHD simulation. We present ongoing 3D simulation with our multidimensional RHD supernova code CHIMERA that includes all of the most important physical components. The 3D simulation will be compared to completed axisymmetric (2D) simulations that have shown robust explosions in agreement with observational measurements. The impact of symmetry (dimension) and its consequences for our understanding of the explosion mechanism will be discussed in the context of current simulations. [Preview Abstract] |
Tuesday, April 8, 2014 11:21AM - 11:33AM |
X8.00004: The Magnetorotational Explosion Mechanism in Full 3D Core-Collapse Supernova Simulations Sherwood Richers, Philipp Moesta, Christian Ott, Anthony Piro, Roland Haas, Kristen Boydstun, Ernazar Abdikamalov, Christian Reisswig, Erik Schnetter We present the first fully 3D general-relativistic magneto-hydrodynamics (GRMHD) simulations of stellar collapse in rapidly rotating, magnetized progenitors using a microphysical equation of state and a Leakage neutrino transport approx\ imation. We perform simulations in 3D both with octant symmetry and with no imposed symmetries of the same 25 $M_\odot$ progenitor. We show that in the simulation without symmetries a kink instability disrupts the initial formation of a\ jet, while octant symmetry allows the jet to stably propagate and leads to a jet-driven explosion. Rising magnetic bubbles expand the shock of the symmetry-free simulations at later times, but the star's ultimate fate is uncertain. [Preview Abstract] |
Tuesday, April 8, 2014 11:33AM - 11:45AM |
X8.00005: Toward Connecting Core-Collapse Supernova Explosions with Observations of their Supernova Remnants Timothy Handy, Tomasz Plewa, Andrzej Odrzywolek We study the process of collapse of a massive star and the following explosion process until the formation of a young supernova remnant in a single simulation. These new models are critically evaluated against a database of core-collapse supernovae (ccSNe) explosion models obtained with a standard supernova code. We develop a multiphysics hydrocode capable of accounting for physics from before collapse occurs until the supernova remnant phase. This enables ccSNe studies with a single code without the need of remapping or transferring data between multiple codes. The code uses a new algorithm to account for the effects of neutrino-matter interaction in the collapsing stellar core. The algorithm uses ray-casting in three dimensions and enables performing collapse and explosion simulations on AMR meshes, including non-radial discretizations. Heating due to radioactive decay, and magnetization of the ejecta are included in the model. The asymmetry of the explosion continues to play a role well beyond the shock breakout phase. In particular, the lateral momentum deposited in the process of shock revival helps shape the supernova ejecta. Another important contributing factor shaping the ejecta is due to radioactive decay of nucleosynthetic products of the explosion. [Preview Abstract] |
Tuesday, April 8, 2014 11:45AM - 11:57AM |
X8.00006: Catching the First Cosmic Explosions: Explosion and Mixing of Pair-Instability Supernovae Ke-Jung Chen, Alexander Heger, Stan Woosley We present multidimensional simulations of the thermonuclear supernovae from massive primordial stars. Numerical and theoretical study of the primordial star formation in the early Universe suggest that these stars could have been very massive. Primordial stars with initial masses of 150-260 solar masses may have died as energetic thermonuclear supernovae, so-called pair-instability supernovae (PSNe). We model the explosion of PSNe by using a new radiation-hydro code, CASTRO and find the fluid instabilities driven by nuclear burning and hydrodynamics during the explosion. For red supergiant models, amplitudes of these instabilities are sufficient to break down the spherical symmetry of the supernova ejecta. [Preview Abstract] |
Tuesday, April 8, 2014 11:57AM - 12:09PM |
X8.00007: ``Pheudo-cyclotron'' radiation of non-relativistic particles in small-scale magnetic turbulence Brett Keenan, Alex Ford, Mikhail V. Medvedev Plasma turbulence in some astrophysical objects (e.g., weakly magnetized collisionless shocks in GRBs and SN) has small-scale magnetic field fluctuations. We study spectral characteristics of radiation produced by particles moving in such turbulence. It was shown earlier that relativistic particles produce jitter radiation, which spectral characteristics are markedly different from synchrotron radiation. Here we study radiation produced by non-relativistic particles. In the case of a homogeneous fields, such radiation is cyclotron and its spectrum consists of just a single harmonic at the cyclotron frequency. However, in the sub-Larmor-scale turbulence, the radiation spectrum is much reacher and reflects statistical properties of the underlying magnetic field. We present both analytical estimates and results of {\it ab initio} numerical simulations. We also show that particle propagation in such turbulence is diffusive and evaluate the diffusion coefficient. We demonstrate that the diffusion coefficient correlates with some spectral parameters. These results can be very valuable for remote diagnostics of laboratory and astrophysical plasmas. [Preview Abstract] |
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