Neutron Star Dynamics in the Era of Gravitational Wave Astronomy

• Applicant: Professor Kostas Kokkotas, Ph.D.
• Subject Area: Astrophysics and Astronomy ; Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: from 2018 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 413873357

• Final Report Year: 2024

Final Report Abstract

In this project, we expanded gravitational wave asteroseismology to include fast rotating neutron stars, taking into account for the first time the contribution of a dynamic spacetime. The results can be useful in modeling and studying gravitational wave signals from merging neutron stars and gravitational collapse. Using the asteroseismological/universal relations that we derived, one can obtain information about the sequence of events, the details of the nuclear equation of state, and other parameters of the neutron stars. Additionally, the universal relations we derived can be used to link observations in the electromagnetic and gravitational wave spectra with the structure of associated objects and the sequence of events during their short but highly dynamic lifespan. Furthermore, we studied the tidal excitation of oscillations in merging neutron stars, which may be responsible for crust yielding and subsequent emission of precursors in the X-ray spectrum. We also quantified the influence of neutron star rotation on the gravitational waveform during the pre-merger phase, as fast rotation can cause significant de-phasing. Finally, by implementing Bayesian and multivariate analysis methods, we were able to derive new asteroseismological relations.

Publications

• Black hole scalarization induced by the spin: 2 +1 time evolution. Phys. Rev. D, 102(10):104027.
  Doneva, Daniela D.; Collodel, Lucas G.; Krüger, Christian J. & Yazadjiev, Stoytcho S.
  
• Dynamics of fast rotating neutron stars: An approach in the Hilbert gauge. Physical Review D, 102(6).
  Krüger, Christian J. & Kokkotas, Kostas D.
  
• Estimates for disk and ejecta masses produced in compact binary mergers. Physical Review D, 101(10).
  Krüger, Christian J. & Foucart, Francois
  
• Fast Rotating Relativistic Stars: Spectra and Stability without Approximation. Physical Review Letters, 125(11).
  Krüger, Christian J. & Kokkotas, Kostas D.
  
• Gravitational Higgs mechanism and resulting observational effects. Physical Review D, 102(12).
  Krall, Verena; Coates, Andrew & Kokkotas, Kostas D.
  
• Precursor flares of short gamma-ray bursts from crust yielding due to tidal resonances in coalescing binaries of rotating, magnetized neutron stars. Physical Review D, 101(8).
  Suvorov, Arthur G. & Kokkotas, Kostas D.
  
• Spin-induced scalarization of Kerr black holes with a massive scalar field. The European Physical Journal C, 80(12).
  Doneva, Daniela D.; Collodel, Lucas G.; Krüger, Christian J. & Yazadjiev, Stoytcho S.
  
• Stability of topological neutron stars. Physical Review D, 102(4).
  Doneva, Daniela D.; Yazadjiev, Stoytcho S. & Kokkotas, Kostas D.
  
• Bayesian inverse problem of rotating neutron stars. Physical Review D, 103(8).
  Völkel, Sebastian H.; Krüger, Christian J. & Kokkotas, Kostas D.
  
• Fast Rotating Neutron Stars: Oscillations and Instabilities. Frontiers in Astronomy and Space Sciences, 8.
  Krüger, Christian J.; Kokkotas, Kostas D.; Manoharan, Praveen & Völkel, Sebastian H.
  
• General-relativistic treatment of tidal g-mode resonances in coalescing binaries of neutron stars – I. Theoretical framework and crust breaking. Monthly Notices of the Royal Astronomical Society, 506(2), 2985-2998.
  Kuan, Hao-Jui; Suvorov, Arthur G. & Kokkotas, Kostas D.
  
• General-relativistic treatment of tidal g-mode resonances in coalescing binaries of neutron stars – II. As triggers for precursor flares of short gamma-ray bursts. Monthly Notices of the Royal Astronomical Society, 508(2), 1732-1744.
  Kuan, Hao-Jui; Suvorov, Arthur G. & Kokkotas, Kostas D.
  
• Oscillation dynamics of scalarized neutron stars. Physical Review D, 103(12).
  Krüger, Christian J. & Doneva, Daniela D.
  
• Precessing magnetars as central engines in short gamma-ray bursts. Monthly Notices of the Royal Astronomical Society, 502(2), 2482-2494.
  Suvorov, A. G. & Kokkotas, K. D.
  
• Universal relations for binary neutron star mergers with long-lived remnants. Physical Review D, 104(2).
  Manoharan, Praveen; Krüger, Christian J. & Kokkotas, Kostas D.
  
• Constraining equation-of-state groups from g-mode asteroseismology. Monthly Notices of the Royal Astronomical Society, 513(3), 4045-4056.
  Kuan, Hao-Jui; Krüger, Christian J.; Suvorov, Arthur G. & Kokkotas, Kostas D.
  
• Constraining the nuclear equation of state from rotating neutron stars. Physical Review D, 105(12).
  Völkel, Sebastian H. & Krüger, Christian J.
  
• f -mode imprints on gravitational waves from coalescing binaries involving aligned spinning neutron stars. Phys. Rev. D, 106(6):064052.
  Kuan, Hao-Jui & Kokkotas, Kostas D.
  
• Quasi-periodic oscillations in precursor flares via seismic aftershocks from resonant shattering. Astronomy & Astrophysics, 664, A177.
  Suvorov, A. G.; Kuan, H. J. & Kokkotas, K. D.
  
• Measuring spin in coalescing binaries of neutron stars that show double precursors. Astronomy & Astrophysics, 676, A59.
  Kuan, Hao-Jui; Suvorov, Arthur G. & Kokkotas, Kostas D.
  
• Neutron stars in Gauss-Bonnet gravity: Nonlinear scalarization and gravitational phase transitions. Physical Review D, 108(4).
  Doneva, Daniela D.; Krüger, Christian J.; Staykov, Kalin V. & Yordanov, Petar Y.
  
• Rapidly rotating neutron stars: Universal relations and EOS inference. Physical Review D, 108(12).
  Krüger, Christian J. & Völkel, Sebastian H.
  
• Finding universal relations using statistical data analysis. Physical Review D, 109(10).
  Manoharan, Praveen & Kokkotas, Kostas D.