How Neutron Star Observations Point Towards Exotic Matter: Existing Explanations and a Prospective Proposal
arXiv:2602.06170 · doi:10.3390/sym18010027
Abstract
Multi-messenger astronomical observations of neutron stars, together with more precise calculations and constraints coming from dense matter microphysics, are generating tension with regard to equations of state models used to describe neutron star cores. Assuming an abrupt first-order phase transition with a slow conversion speed between phases, we propose different slow stable hybrid star configurations aiming to reconcile all current constraints simultaneously; within this framework, we also introduce a novel non-CSS parametrization to the quark matter equation of state and discuss its strengths and limitations. We analyze our model results in conjunction with a review of other relevant theoretical possibilities existing in the literature. We found that modern neutron star observations seem to favor the existence of some type of exotic matter in the neutron star cores; in particular, our slow stable hybrid star scenario remains a proposal capable of satisfying these constraints. However, due both to the existing skepticism regarding some of the adopted hypotheses in most extreme neutron star measurements and to the precise adjustment needed for the equation-of-state parameters, significant tension and open questions remain.
This article belongs to the Special Issue 'Microphysics Meets Astrophysics: Understanding Dense Matter Through Compact Objects' of the Symmetry journal
References in corpus (101)
- 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
- GW170817: Measurements of Neutron Star Radii and Equation of State
- PSR J0030+0451 Mass and Radius from NICER Data and Implications for the Properties of Neutron Star Matter
- A NICER View of PSR J0030+0451: Millisecond Pulsar Parameter Estimation
- GW190425: Observation of a Compact Binary Coalescence with Total Mass
- Relativistic Shapiro delay measurements of an extremely massive millisecond pulsar
- NJL-model analysis of dense quark matter
- Masses, Radii, and Equation of State of Neutron Stars
- A NICER View of the Massive Pulsar PSR J0740+6620 Informed by Radio Timing and XMM-Newton Spectroscopy
- Refined Mass and Geometric Measurements of the High-Mass PSR J0740+6620
- From hadrons to quarks in neutron stars: a review
- Hybrid stars that masquerade as neutron stars
- Evidence for quark-matter cores in massive neutron stars
- On the Phase Diagram of QCD
- The NANOGrav 11-year Data Set: High-precision timing of 45 Millisecond Pulsars
- PSR J0952-0607: The Fastest and Heaviest Known Galactic Neutron Star
- Color superconducting quark matter
- Crystalline Color Superconductivity
- Generic conditions for stable hybrid stars
- Continuity of Quark and Hadron Matter
- Neutron star radii and crusts: uncertainties and unified equations of state
- Sound velocity bound and neutron stars
- Constraint on the maximum mass of neutron stars using GW170817 event
- A NICER View of the Nearest and Brightest Millisecond Pulsar: PSR J0437$\unicode{x2013}$4715
- The phase diagram of neutral quark matter: Self-consistent treatment of quark masses
- Compact stars with sequential QCD phase transitions
- A Novel Approach to Model Hybrid Stars
- Can very compact and very massive neutron stars both exist?
- Limiting masses and radii of neutron stars and their implications
- Hadron-Quark Crossover and Massive Hybrid Stars
- Properties of the QCD Matter -- An Experimental Review of Selected Results from RHIC BES Program
- Density Discontinuity of a Neutron Star and Gravitational Waves
- Quark deconfinement in high-mass neutron stars
- Phase transition effects on the dynamical stability of hybrid neutron stars
- Third family of compact stars within a nonlocal chiral quark model equation of state
- Phase Transitions in Neutron Stars and Maximum Masses
- The Surface Tension of Quark Matter in a Geometrical Approach
- Non-radial oscillation modes as a probe of density discontinuities in neutron stars
- A Parametrized Equation of State for Neutron Star Matter with Continuous Sound Speed
- A NICER View of PSR J12311411: A Complex Case
- What is the nature of the HESS J1731-347 compact object?
- Phase diagram and surface tension in the three-flavor Polyakov-quark-meson model
- Equilibrium and stability of charged strange quark stars
- Phase transitions in dense matter and the maximum mass of neutron stars
- Evidence against a strong first-order phase transition in neutron star cores: impact of new data
- The Constant-Sound-Speed parameterization for NJL models of quark matter in hybrid stars
- Magnetars: a short review and some sparse considerations
- Phase transitions in neutron stars and their links to gravitational waves
- First Order Phase Transitions in Neutron star Matter: Droplets and Coherent Neutrino Scattering
- Hybrid and quark star matter based on a non-perturbative equation of state
- Oscillation modes of hybrid stars within the relativistic Cowling approximation
- Delta baryons and diquark formation in the cores of neutron stars
- Modified MIT bag Models -- part I: Thermodynamic consistency, stability windows and symmetry group
- Classifications of Twin Star Solutions for a Constant Speed of Sound Parameterized Equation of State
- Discontinuity gravity modes in hybrid stars: assessing the role of rapid and slow phase conversions
- Quark-hadron continuity beyond Ginzburg-Landau paradigm
- Constraining self-interacting fermionic dark matter in admixed neutron stars using multimessenger astronomy
- Do Central Compact Objects have Carbon Atmospheres?
- Constraining the Properties of the Thermonuclear Burst Oscillation Source XTE J1814-338 Through Pulse Profile Modelling
- Bayesian uncertainty quantification of perturbative QCD input to the neutron-star equation of state
- Magnetised hybrid stars: effects of slow and rapid phase transitions at the quark-hadron interface
- Non-strange quark stars from NJL model with proper-time regularisation
- Radial oscillations and stability of multiple-fluid compact stars
- Two novel approaches to the hadron-quark mixed phase in compact stars
- A model-agnostic analysis of hybrid stars with reactive interfaces
- Heavy hybrid stars from multi-quark interactions
- Recovering the conformal limit of color superconducting quark matter within a confining density functional approach
- Quark matter in Neutron Stars within the Field Correlator Method
- Hybrid stars with sequential phase transitions: the emergence of the g mode
- Is the compact object associated with HESS J1731-347 a strange quark star?
- Probing elastic quark phases in hybrid stars with radius measurements
- Constant entropy hybrid stars: a first approximation of cooling evolution
- Framework for phase transitions between the Maxwell and Gibbs constructions
- Relativistic hybrid stars with sequential first-order phase transitions in light of multimessenger constraints
- Two first-order phase transitions in hybrid compact stars: higher-order multiplet stars, reaction modes and intermediate conversion speeds
- Dense Matter in Neutron Stars with eXTP
- Could a slow stable hybrid star explain the central compact object in HESS~J1731-347?
- Impact of slow conversions on hybrid stars with sequential QCD phase transitions
- XTE J1814-338: A potential hybrid star candidate
- Effects of Hadron-Quark Phase Transitions in Hybrid Stars within the NJL Model
- Asteroseismology using quadrupolar f-modes revisited: breaking of universal relationships in the slow hadron-quark conversion scenario
- Speed of sound in dense matter and two families of compact stars
- Breaking of universal relationships of axial wI-modes in hybrid stars: rapid and slow hadron-quark conversion scenarios
- Thermal twin stars within a hybrid equation of state based on a nonlocal chiral quark model compatible with modern astrophysical observations
- Radial Mode Stability of Two-Fluid Neutron Stars
- Non-equilibrium effects on stability of hybrid stars with first-order phase transitions
- Hybrid stars with reactive interfaces: analysis within the Nambu-Jona-Lasinio model
- Quark-hadron pasta phase in neutron stars: the role of medium-dependent surface and curvature tensions
- Modern nuclear and astrophysical constraints of dense matter in a renormalized chiral approach
- The study of nonstrange quark stars within a modified NJL model
- Strange star equations of state revisited
- Signature of hadron-quark crossover in binary-neutron-star mergers
- Constraining Bag constant for Hybrid Neutron stars
- Hybrid stars within the framework of the Sigma-Omega-Rho model combined with the MIT and NJL models
- Towards a unified hadron-quark equation of state for neutron stars within the relativistic mean-field model
- Strange quark stars: the role of excluded volume effects
- Compact Stars as Hideouts For Color-spin-locked Quark Matter: Implications for Powering High-energy Electromagnetic Emissions
- Consistent crust-core interpolation and its effect on non-radial neutron star oscillations
- Can a hybrid star with constant sound speed parametrization explain the new NICER mass-radius measurements ?