Characterizing the breakdown of quasi-universality in the post-merger gravitational waves from binary neutron star mergers

Abstract

The post-merger gravitational wave (GW) emission from a binary neutron star merger is expected to provide exciting new constraints on the dense-matter equation of state (EoS). Such constraints rely, by and large, on the existence of quasi-universal relations, which relate the peak frequencies of the post-merger GW spectrum to properties of the neutron star structure in a model-independent way. In this work, we report on violations of existing quasi-universal relations between the peak spectral frequency, f_2, and the stellar radius, for EoSs models with backwards-bending slopes in their mass-radius relations (such that the radius increases at high masses). The violations are extreme, with variations in f_2 of up to ~600 Hz between EoSs that predict the same radius for a 1.4 Msun neutron star, but that have significantly different radii at higher masses. Quasi-universality can be restored by adding in a second parameter to the fitting formulae that depends on the slope of the mass-radius curve. We further find strong evidence that quasi-universality is better maintained for the radii of very massive stars (with masses 2 Msun). Both statements imply that f_2 is mainly sensitive to the high-density EoS. Combined with observations of the binary neutron star inspiral, these generalized quasi-universal relations can be used to simultaneously infer the characteristic radius and slope of the neutron star mass-radius relation.

11 pages, 5 figures. Equal contribution

References in corpus (15)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• Shapiro delay measurement of a two solar mass neutron star
• A Massive Pulsar in a Compact Relativistic Binary
• A NICER View of the Massive Pulsar PSR J0740+6620 Informed by Radio Timing and XMM-Newton Spectroscopy
• Constraints on a phenomenologically parameterized neutron-star equation of state
• Spectral properties of the post-merger gravitational-wave signal from binary neutron stars
• New Hyperon Equations of State for Supernovae and Neutron Stars in Density-dependent Hadron Field Theory
• The Dynamics of Binary Neutron Star Mergers and of GW170817
• A New Open-Source Nuclear Equation of State Framework based on the Liquid-Drop Model with Skyrme Interaction
• Finite-temperature extension for cold neutron star equations of state
• The slope, the hill, the drop, and the swoosh: Learning about the nuclear matter equation of state from the binary Love relations
• Probing the equation of state of neutron star matter with gravitational waves from binary inspirals in light of GW170817: a brief review
• Impact of the nuclear symmetry energy on the post-merger phase of a binary neutron star coalescence
• The Radius of PSR J0740+6620 from NICER and XMM-Newton Data
• Constraints on the Neutron Star Equation of State from GW170817

Cited by in corpus (5)

• Emergence of microphysical bulk viscosity in binary neutron star post-merger dynamics
• Binary neutron star mergers as a probe of quark-hadron crossover equations of state
• Degeneracy in the inference of phase transitions in the neutron star equation of state from gravitational wave data
• Needle in a Bayes Stack: a Hierarchical Bayesian Method for Constraining the Neutron Star Equation of State with an Ensemble of Binary Neutron Star Post-merger Remnants
• Effects of Onset of Phase Transition on Binary Neutron Star Mergers