Jacobi, Maximilian (2023)
Neutron star mergers:
Mass ejection and the role of the nuclear equation of state.
Technische Universität Darmstadt
doi: 10.26083/tuprints-00024781
Dissertation, Erstveröffentlichung, Verlagsversion
Kurzbeschreibung (Abstract)
Binary neutron star (BNS) mergers are fascinating astrophysical events that are likely responsible for the production of about half of the heavy elements in the universe. The nuclear equation of state (EOS) plays a crucial role in the dynamics of BNS mergers. However, it is highly uncertain due to the lack of knowledge on nuclear interaction at high densities. Binary neutron star mergers emit gravitational waves (GWs) and produce an optical transient called kilonova (KN) which is powered by the radioactive decay of freshly synthesized heavy nuclei. This makes them ideal sources for multi-messenger observations providing valuable information about the dynamics of the merger and the properties of the ejected matter. By comparing the predictions of numerical simulations of BNS mergers with multi-messenger observations, it is possible to derive constraints for the EOS at high densities. This makes BNS mergers incredibly useful laboratories for studying the EOS at very high densities. The first part of this thesis investigates the influence of the EOS on BNS mergers in a systematic way. We perform three-dimensional (3D) general-relativistic hydrodynamics simulations with eight different EOS models, where we systematically vary the effective mass, incompressibility, symmetry energy, and saturation point of nuclear matter. By analyzing the relationship of these nuclear matter properties with the evolution of the merger remnant, post-merger GW signal, and ejecta, we uncover novel insights into the connection between the EOS and the outcome of BNS mergers. We find, that the deformation of the massive neutron star (NS) after the merger is related to the incompressibility, which has implications for the post-merger GW signal and mass ejection. Furthermore, we identify correlations of the tidal and shock-heated dynamical ejecta components with the incompressibility and effective mass. The second part of this work concerns long-term simulations of the accretion disk phase of BNS mergers. The largest component of the ejecta in a BNS merger originates from the post-merger accretion disk. Thus, it is necessary to perform numerical simulations for multiple seconds to obtain a complete picture of the ejected matter. However, running 3D simulations for such long times requires a huge amount of computational resources. We circumvent this issue by simulating the accretion-disk phase of the merger in two dimensions (2D) while assuming axisymmetry which greatly reduces the computational cost of the simulations. To consistently link a 2D simulation of the accretion disk to a 3D simulation of the merger, we create the 2D initial data using the configuration of the merger remnant from the 3D simulation. We describe the methods we use for the axisymmetric simulations and the creation of the initial data. Moreover, we perform several tests of these methods and discuss the results.
Typ des Eintrags: | Dissertation | ||||
---|---|---|---|---|---|
Erschienen: | 2023 | ||||
Autor(en): | Jacobi, Maximilian | ||||
Art des Eintrags: | Erstveröffentlichung | ||||
Titel: | Neutron star mergers: Mass ejection and the role of the nuclear equation of state | ||||
Sprache: | Englisch | ||||
Referenten: | Arcones, Prof. Dr. Almudena ; Hebeler, Dr. habil. Kai | ||||
Publikationsjahr: | 15 Dezember 2023 | ||||
Ort: | Darmstadt | ||||
Kollation: | xi, 113 Seiten | ||||
Datum der mündlichen Prüfung: | 24 April 2023 | ||||
DOI: | 10.26083/tuprints-00024781 | ||||
URL / URN: | https://tuprints.ulb.tu-darmstadt.de/24781 | ||||
Kurzbeschreibung (Abstract): | Binary neutron star (BNS) mergers are fascinating astrophysical events that are likely responsible for the production of about half of the heavy elements in the universe. The nuclear equation of state (EOS) plays a crucial role in the dynamics of BNS mergers. However, it is highly uncertain due to the lack of knowledge on nuclear interaction at high densities. Binary neutron star mergers emit gravitational waves (GWs) and produce an optical transient called kilonova (KN) which is powered by the radioactive decay of freshly synthesized heavy nuclei. This makes them ideal sources for multi-messenger observations providing valuable information about the dynamics of the merger and the properties of the ejected matter. By comparing the predictions of numerical simulations of BNS mergers with multi-messenger observations, it is possible to derive constraints for the EOS at high densities. This makes BNS mergers incredibly useful laboratories for studying the EOS at very high densities. The first part of this thesis investigates the influence of the EOS on BNS mergers in a systematic way. We perform three-dimensional (3D) general-relativistic hydrodynamics simulations with eight different EOS models, where we systematically vary the effective mass, incompressibility, symmetry energy, and saturation point of nuclear matter. By analyzing the relationship of these nuclear matter properties with the evolution of the merger remnant, post-merger GW signal, and ejecta, we uncover novel insights into the connection between the EOS and the outcome of BNS mergers. We find, that the deformation of the massive neutron star (NS) after the merger is related to the incompressibility, which has implications for the post-merger GW signal and mass ejection. Furthermore, we identify correlations of the tidal and shock-heated dynamical ejecta components with the incompressibility and effective mass. The second part of this work concerns long-term simulations of the accretion disk phase of BNS mergers. The largest component of the ejecta in a BNS merger originates from the post-merger accretion disk. Thus, it is necessary to perform numerical simulations for multiple seconds to obtain a complete picture of the ejected matter. However, running 3D simulations for such long times requires a huge amount of computational resources. We circumvent this issue by simulating the accretion-disk phase of the merger in two dimensions (2D) while assuming axisymmetry which greatly reduces the computational cost of the simulations. To consistently link a 2D simulation of the accretion disk to a 3D simulation of the merger, we create the 2D initial data using the configuration of the merger remnant from the 3D simulation. We describe the methods we use for the axisymmetric simulations and the creation of the initial data. Moreover, we perform several tests of these methods and discuss the results. |
||||
Alternatives oder übersetztes Abstract: |
|
||||
Status: | Verlagsversion | ||||
URN: | urn:nbn:de:tuda-tuprints-247811 | ||||
Sachgruppe der Dewey Dezimalklassifikatin (DDC): | 500 Naturwissenschaften und Mathematik > 530 Physik | ||||
Fachbereich(e)/-gebiet(e): | 05 Fachbereich Physik 05 Fachbereich Physik > Institut für Kernphysik 05 Fachbereich Physik > Institut für Kernphysik > Theoretische Kernphysik 05 Fachbereich Physik > Institut für Kernphysik > Theoretische Kernphysik > Kernphysik und Nukleare Astrophysik |
||||
TU-Projekte: | DFG|SFB1245|B07_SFB1245 DFG|SFB1245|B06_B07_SFB1245 |
||||
Hinterlegungsdatum: | 15 Dez 2023 13:28 | ||||
Letzte Änderung: | 19 Dez 2023 08:24 | ||||
PPN: | |||||
Referenten: | Arcones, Prof. Dr. Almudena ; Hebeler, Dr. habil. Kai | ||||
Datum der mündlichen Prüfung / Verteidigung / mdl. Prüfung: | 24 April 2023 | ||||
Export: | |||||
Suche nach Titel in: | TUfind oder in Google |
Frage zum Eintrag |
Optionen (nur für Redakteure)
Redaktionelle Details anzeigen |