Simulating Magnetized Neutron Stars with S P EC Curran D. Muhlberger curran@astro.cornell.edu Department of Physics, Cornell University 15th East Coast Gravity Meeting April 21, 2012
Astrophysics Numerics Status Compact Binaries Isolated Stars Compact Binaries Why add B-fields to NS-NS and BH-NS simulations? Magnetic Effects None during inspiral a Determine accretion rate Field amplification during merger Enable and power GRBs a Giacomazzo et al. 2009 Curran D. Muhlberger Simulating Magnetized Neutron Stars with S P EC
Astrophysics Numerics Status Compact Binaries Isolated Stars Isolated Stars Why are single stars interesting? Used to Study Core collapse SN remnants Low-mass NS-NS merger remnants Magnetic Effects Collapse of spheroidal remnants Instabilities affect GWs Curran D. Muhlberger Simulating Magnetized Neutron Stars with S P EC
Astrophysics Numerics Status Compact Binaries Isolated Stars The Low- T / | W | Instability Core-Collapse Supernovae Remnants Dynamical m = 2 instabilities produce strong GWs Not susceptible to dynamical bar-mode instability Differential rotation enables shear instability, but ... Magnetic fields may suppress this instability a a Fu & Lai 2011 Goal: Investigate low- T / | W | instability in full GRMHD Curran D. Muhlberger Simulating Magnetized Neutron Stars with S P EC
Astrophysics Numerics Status S P EC GRMHD The Spectral Einstein Code Numerical Methods Pseudospectral method with excision for smooth spacetime HRSC FV scheme for shock-prone matter Strengths: high efficiency in vacuum regions; high resolution fluid grid S P EC is the product of a collaboration between Caltech, Cornell, CITA, and WSU Curran D. Muhlberger Simulating Magnetized Neutron Stars with S P EC
Astrophysics Numerics Status S P EC GRMHD Generally Relativistic Magnetohydrodynamics Shock Treatment Can evolve B-field with a generalization of WENO reconstruction HLL Riemann solver ∂ t B = ∇ × ( v × B ) , Ideal MHD but the equations are: B-field confined to 1 Not flux-conservative matter 2 Overconstrained Perfect conductivity Curran D. Muhlberger Simulating Magnetized Neutron Stars with S P EC
Astrophysics Numerics Status S P EC GRMHD Maintaining the Solenoidal Constraint Goal: ∇ · B = 0 Approaches Evolve B with Constrained Transport Guarantees ∂ t ( ∇ · B ) = 0, but . . . Monopoles created during interpolation Add Divergence Cleaning a Reduces divergence over time, but . . . Damping too slow during merger Evolve A with Constrained Transport In progress a Implemented by Francois Foucart Curran D. Muhlberger Simulating Magnetized Neutron Stars with S P EC
Astrophysics Numerics Status Current Capabilities Future Work Current Capabilities Magnetized BH-NS inspiral with a poloidal seed field Curran D. Muhlberger Simulating Magnetized Neutron Stars with S P EC
Astrophysics Numerics Status Current Capabilities Future Work Future Work Several researchers are investigating magnetized systems in S P EC, but I am personally focused on the following: Projects in Progress Distortion Parameter: Plus Polarization 2 Investigate effects of SLy; Â =1; β =0.2 1.5 B-field on low- T / | W | 1 instability 0.5 η + × 103 0 Follow B-fields through -0.5 -1 BH-NS merger -1.5 -2 Add B-fields to NS-NS 0 2 4 6 8 10 12 14 simulations Time [ms] Curran D. Muhlberger Simulating Magnetized Neutron Stars with S P EC
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