Magnetohydrodynamics simulations performed in full general relativity represent the ideal tool to unravel the dynamics of binary neutron star (BNS) mergers as well as the postmerger evolution of the resulting remnant object. This approach allows us to study in particular (i) the magnetic field amplification and the possible formation of collimated relativistic outflows or jets, which is fundamental to make the connection with the resulting short gammaray bursts (SGRBs), (ii) the associated gravitational wave (GW) emission, and (iii) the properties of the massive and metastable neutron star remnant before it eventually collapses into a black hole (BH), depending on the properties of the progenitor binary system. In this Thesis we carry out this type of investigation for two models (with mass ratio $q=0.9$ and $q=1.0$) consistent with the observed properties of GW170817, the first BNS merger observed in GWs by the Advanced LIGO and Virgo interferometers. Specifically, we use the Lorene code to build the initial data for an irrotational BNS model with the same total mass of GW170817, where we employ the APR4 equation of state for the description of matter at supranuclear densities. We further assume a high initial magnetization corresponding to a maximum magnetic field strength of $5\times10^{15} \, \text{G}$. This system is then evolved up to merger and beyond with the numerical relativity evolution codes Einstein Toolkit and WhiskyMHD. Our results provide important hints for the interpretation of the multimessenger observation of this breakthrough event.
Investigating the binary neutron star merger event GW170817 via general relativistic magnetohydrodynamics simulations
Griggio, Massimo
2020/2021
Abstract
Magnetohydrodynamics simulations performed in full general relativity represent the ideal tool to unravel the dynamics of binary neutron star (BNS) mergers as well as the postmerger evolution of the resulting remnant object. This approach allows us to study in particular (i) the magnetic field amplification and the possible formation of collimated relativistic outflows or jets, which is fundamental to make the connection with the resulting short gammaray bursts (SGRBs), (ii) the associated gravitational wave (GW) emission, and (iii) the properties of the massive and metastable neutron star remnant before it eventually collapses into a black hole (BH), depending on the properties of the progenitor binary system. In this Thesis we carry out this type of investigation for two models (with mass ratio $q=0.9$ and $q=1.0$) consistent with the observed properties of GW170817, the first BNS merger observed in GWs by the Advanced LIGO and Virgo interferometers. Specifically, we use the Lorene code to build the initial data for an irrotational BNS model with the same total mass of GW170817, where we employ the APR4 equation of state for the description of matter at supranuclear densities. We further assume a high initial magnetization corresponding to a maximum magnetic field strength of $5\times10^{15} \, \text{G}$. This system is then evolved up to merger and beyond with the numerical relativity evolution codes Einstein Toolkit and WhiskyMHD. Our results provide important hints for the interpretation of the multimessenger observation of this breakthrough event.File  Dimensione  Formato  

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https://hdl.handle.net/20.500.12608/23046