Neutron Stars and Gravitational Waves: the Key Role of Nuclear Equation of State

Abstract

Neutron stars are the densest known objects in the universe and an ideal laboratory for the strange physics of super-condensed matter. Theoretical studies in connection with recent observational data of isolated neutron stars, as well as binary neutron stars systems, offer an excellent opportunity to provide robust solutions on the dense nuclear problem. In the present work, we review recent studies concerning the applications of various theoretical nuclear models on a few recent observations of binary neutron stars or neutron-star--black-hole systems. In particular, using a simple and well-established model, we parametrize the stiffness of the equation of state with the help of the speed of sound. Moreover, in comparison to the recent observations of two events by LIGO/VIRGO collaboration, GW170817 and GW190425, we suggest possible robust constraints. We also concentrate our theoretical study on the resent observation of a compact object with mass~$\sim 2.59_{-0.09}^{+0.08}{M}_{\odot }$ (GW190814 event), as a component of a system where the main companion was a black hole with mass $\sim 23M_{\odot }$. There is scientific debate concerning the identification of the low mass component, as it falls into the neutron-star--black-hole mass gap. This is an important issue since understanding the nature of GW190814 event will offer rich information concerning the upper limit of the speed of sound in dense matter and the possible phase transition into other degrees of freedom. We systematically study the tidal deformability of a possible high-mass candidate existing as an individual star or as a component in a binary neutron star system. Finally, we provide some applications of equations of state of hot, dense nuclear matter in hot neutron stars, protoneutron stars, and binary neutron star merger remnants.

review article: 42 pages, 16 figures, 5 tables; accepted to be published in Foundations. v2: changes to match the published review article

References in corpus (39)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• A Massive Pulsar in a Compact Relativistic Binary
• GW190814: Gravitational Waves from the Coalescence of a 23 M${}_{\odot }$ Black Hole with a 2.6 M${}_{\odot }$ Compact Object
• PSR J0030+0451 Mass and Radius from NICER Data and Implications for the Properties of Neutron Star Matter
• Tidal Love numbers of neutron stars
• Constraining neutron star tidal Love numbers with gravitational wave detectors
• GW170817: Joint Constraint on the Neutron Star Equation of State from Multimessenger Observations
• Nonparametric constraints on neutron star matter with existing and upcoming gravitational wave and pulsar observations
• Sound velocity bound and neutron stars
• Neutron star tidal deformability and equation of state constraints
• Testing Approximations of Thermal Effects in Neutron Star Merger Simulations
• The Dynamics of Binary Neutron Star Mergers and of GW170817
• Reconstructing the neutron-star equation of state with gravitational-wave detectors from a realistic population of inspiralling binary neutron stars
• A lower bound on the maximum mass if the secondary in GW190814 was once a rapidly spinning neutron star
• Constraining the High-Density Behavior of Nuclear Symmetry Energy with the Tidal Polarizability of Neutron Stars
• Neutron Star Equation of State in light of GW190814
• Revisiting the lower bound on tidal deformability derived by AT 2017gfo
• A new temperature dependent hyperonic equation of state: application to rotating neutron star models and I-Q-relations
• A Second Relativistic Mean Field and Virial Equation of State for Astrophysical Simulations
• Finite-temperature extension for cold neutron star equations of state
• On the stability and maximum mass of differentially rotating relativistic stars
• Hybrid equation of state approach in binary neutron-star merger simulations
• Gravitational waves or deconfined quarks: what causes the premature collapse of neutron stars born in short gamma-ray bursts?
• Speed of sound constraints from tidal deformability of neutron stars
• Updated Parameter Estimates for GW190425 Using Astrophysical Arguments and Implications for the Electromagnetic Counterpart
• Probing the nuclear equation of state from the existence of a $\sim 2.6M_{\odot }$ neutron star: the GW190814 puzzle
• Thermal states of neutron stars with a consistent model of interior
• Effects of isospin and momentum dependent interactions on liquid-gas phase transition in hot asymmetric nuclear matter
• Recognizing black holes in gravitational-wave observations: Challenges in telling apart impostors in mass-gap binaries
• Comment on "Tidal Love numbers of neutron and self-bound quark stars"
• Thermodynamical Description of Hot, Rapidly Rotating Neutron Stars, Protoneutron Stars, and Neutron Star Merger Remnants
• Temperature and momentum dependence of single-particle properties in hot asymmetric nuclear matter
• Speed of sound constraints on maximally rotating neutron stars
• Great Impostors: Extremely Compact, Merging Binary Neutron Stars in the Mass Gap Posing as Binary Black Holes
• Nuclear matter at finite temperature and static properties of proto-neutron star
• Cooling of hybrid neutron stars with microscopic equations of state
• Properties of binary components and remnant in GW170817 using equations of state in finite temperature field theory models
• Accurate nuclear symmetry energy at finite temperature within a BHF approach
• Temperature effects on the neutron matter equation of state obtained from chiral effective field theory

Cited by in corpus (5)

• Twin stars as probes of the nuclear equation of state: effects of rotation through the PSR J0952-0607 pulsar and constraints via the tidal deformability from the GW170817 event
• Impact of The Newly Revised Gravitational Redshift of X-ray Burster GS 1826-24 on The Equation of State of Supradense Neutron-Rich Matter
• Rotating Love: The dynamical tides of spinning Newtonian stars
• Thermal effects on tidal deformability in the last orbits of an inspiraling binary neutron star system
• Dipole Polarizability of Finite Nuclei as a Probe of Neutron Stars