TY - JOUR
T1 - A magnetar engine for short GRBs and kilonovae
AU - Mösta, Philipp
AU - Radice, David
AU - Haas, Roland
AU - Schnetter, Erik
AU - Bernuzzi, Sebastiano
N1 - Publisher Copyright:
© 2020 Institute of Physics Publishing. All rights reserved.
PY - 2020/10/1
Y1 - 2020/10/1
N2 - We investigate the influence of magnetic fields on the evolution of binary neutron star (BNS) merger remnants via three-dimensional (3D) dynamical-spacetime general-relativistic magnetohydrodynamic (MHD) simulations. We evolve a post-merger remnant with an initial poloidal magnetic field, resolve the magnetoturbulence driven by shear flows, and include a microphysical finite-temperature equation of state. A neutrino leakage scheme that captures the overall energetics and lepton number exchange is also included. We find that turbulence induced by the magnetorotational instability in the hypermassive neutron star (HMNS) amplifies magnetic field to beyond magnetar strength (1015 G). The ultra-strong toroidal field is able to launch a relativistic jet from the HMNS. We also find a magnetized wind that ejects neutron-rich material with a rate of Mej ≃ 1 × 10-1M⊙ s- 1. The total ejecta mass in our simulation is 5 ×10-3Me. This makes the ejecta from the HMNS an important component in BNS mergers and a promising source of r-process elements that can power a kilonova. The jet from the HMNS reaches a terminal Lorentz factor of ∼5 in our highest-resolution simulation. The formation of this jet is aided by neutrino cooling preventing the accretion disk from protruding into the polar region. As neutrino pair-annihilation and radiative processes in the jet (which were not included in the simulations) will boost the Lorentz factor in the jet further, our simulations demonstrate that magnetars formed in BNS mergers are a viable engine for short gamma-ray bursts.
AB - We investigate the influence of magnetic fields on the evolution of binary neutron star (BNS) merger remnants via three-dimensional (3D) dynamical-spacetime general-relativistic magnetohydrodynamic (MHD) simulations. We evolve a post-merger remnant with an initial poloidal magnetic field, resolve the magnetoturbulence driven by shear flows, and include a microphysical finite-temperature equation of state. A neutrino leakage scheme that captures the overall energetics and lepton number exchange is also included. We find that turbulence induced by the magnetorotational instability in the hypermassive neutron star (HMNS) amplifies magnetic field to beyond magnetar strength (1015 G). The ultra-strong toroidal field is able to launch a relativistic jet from the HMNS. We also find a magnetized wind that ejects neutron-rich material with a rate of Mej ≃ 1 × 10-1M⊙ s- 1. The total ejecta mass in our simulation is 5 ×10-3Me. This makes the ejecta from the HMNS an important component in BNS mergers and a promising source of r-process elements that can power a kilonova. The jet from the HMNS reaches a terminal Lorentz factor of ∼5 in our highest-resolution simulation. The formation of this jet is aided by neutrino cooling preventing the accretion disk from protruding into the polar region. As neutrino pair-annihilation and radiative processes in the jet (which were not included in the simulations) will boost the Lorentz factor in the jet further, our simulations demonstrate that magnetars formed in BNS mergers are a viable engine for short gamma-ray bursts.
KW - Astrophysical fluid dynamics (101)
KW - General relativity (641)
KW - High energy astrophysics (739)
KW - Jets (870)
KW - Magnetohydrodynamics (1964)
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U2 - 10.3847/2041-8213/abb6ef
DO - 10.3847/2041-8213/abb6ef
M3 - Article
AN - SCOPUS:85092928175
SN - 2041-8205
VL - 901
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 2
ER -