Causality anchored to χEFT at low density implies the closed-form bound R(2.0 M_⊙) ≤ 1.16 R(1.4 M_⊙) − 1.1 km for neutron stars sharing one causal EoS, saturated by an analytic one-parameter family.
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A NICER View of the Massive Pulsar PSR J0740+6620 Informed by Radio Timing and XMM-Newton Spectroscopy
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abstract
We report on Bayesian estimation of the radius, mass, and hot surface regions of the massive millisecond pulsar PSR J0740$+$6620, conditional on pulse-profile modeling of Neutron Star Interior Composition Explorer X-ray Timing Instrument (NICER XTI) event data. We condition on informative pulsar mass, distance, and orbital inclination priors derived from the joint NANOGrav and CHIME/Pulsar wideband radio timing measurements of arXiv:2104.00880. We use XMM European Photon Imaging Camera spectroscopic event data to inform our X-ray likelihood function. The prior support of the pulsar radius is truncated at 16 km to ensure coverage of current dense matter models. We assume conservative priors on instrument calibration uncertainty. We constrain the equatorial radius and mass of PSR J0740$+$6620 to be $12.39_{-0.98}^{+1.30}$ km and $2.072_{-0.066}^{+0.067}$ M$_{\odot}$ respectively, each reported as the posterior credible interval bounded by the 16% and 84% quantiles, conditional on surface hot regions that are non-overlapping spherical caps of fully-ionized hydrogen atmosphere with uniform effective temperature; a posteriori, the temperature is $\log_{10}(T$ [K]$)=5.99_{-0.06}^{+0.05}$ for each hot region. All software for the X-ray modeling framework is open-source and all data, model, and sample information is publicly available, including analysis notebooks and model modules in the Python language. Our marginal likelihood function of mass and equatorial radius is proportional to the marginal joint posterior density of those parameters (within the prior support) and can thus be computed from the posterior samples.
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representative citing papers
A minimal dark matter model with one complex scalar carrying B and L numbers, stabilized by proton stability, with mass near the proton mass and relic density from UV freeze-in.
A redefinition of the symmetry energy expansion that incorporates finite strangeness consistent with SU(3) flavor symmetry and remains valid beyond typical neutron-star central densities.
Lambda hyperons equilibrate rapidly in post-collapse proto-neutron stars through nonleptonic NN to N Lambda processes and enhance low-energy muon neutrino opacities beyond nucleonic contributions.
Slow hadron-quark conversion in hybrid neutron stars creates extended stable 'waterfall' branches, reviving stiff hadronic equations of state that rapid-conversion analyses reject.
Amortized neural posterior estimation reproduces nested sampling constraints on RMF couplings for neutron-star EOS with no bias and generates 30,000 samples in 2.5 seconds.
A first-principles FRG approach to two-flavor QCD derives low-energy constants for the pion, sigma-meson and scalar diquark without parameters beyond QCD itself, including new diquark properties for color-superconducting models.
Bayesian analysis of astrophysical and laboratory data favors the two-families scenario of coexisting hadronic and strange quark stars over the one-family scenario.
A conservative f(R,T) gravity reformulation decouples the gravitational sector from the microphysical equation of state, enabling computation of neutron star mass-radius relations and tidal deformabilities that satisfy current astrophysical constraints.
A physics-informed Bayesian neural network learns neutron-star equations of state from theoretical priors and constraints, then generates posterior mass-radius and mass-tidal-deformability distributions consistent with NICER radii and 2-solar-mass limits.
Causal viscous relativistic hydrodynamics applied to neutron stars yields new axial mode families without perfect-fluid counterparts, including mode avoidance and long-lived modes.
RGOPT-resummed NNLO pQCD EoS for massive quarks in beta equilibrium is fitted and applied to construct pure quark stars (X=3.08-3.58) and hybrid stars (X~2-2.98) compatible with PSR J0740+6620 and GW190814.
Long-term numerical-relativity runs find isolated neutron stars with an external dipole relax to a stable mixed poloidal-toroidal field with toroidal energy ≲10% after Tayler saturation.
Bayesian analysis finds that the likely ranges of light dark-matter fermion mass and exponential density-profile parameter in hyperon-containing neutron stars are nearly independent of the hadronic model for symmetry-energy slopes between 40 and 58 MeV, with HESS J1731-347 and GW170817 data playing,
Axial modes of anisotropic neutron stars are integrated numerically for realistic EOS; frequency falls with mass, damping time rises, and scaled quantities follow a near-universal quadratic in compactness that is largely EOS-insensitive but mildly model-dependent.
Hybrid star model with core quark pasta pinning superfluid vortices produces glitch amplitudes ΔΩ/Ω of order 10^{-6} matching Vela-like pulsar observations.
Hybrid neutron-star equations of state remain sensitive to the low-density nucleonic model at transition densities around 2ρ₀, with model spread in radius and tidal deformability exceeding observational uncertainty by factors of ~1.8 and ~1.4.
Vector-portal fermionic dark matter softens or stiffens the neutron-star equation of state depending on Z' mass, producing mass-radius and tidal-deformability signatures constrained by GW170817 and NICER.
Roughly half of realistic neutron-star equations of state produce stars with negative Ricci scalar inside, and an improved analytic fit links gravitational mass M to baryonic mass Mb with maximum 3 percent variance.
Dark matter cores heat baryonic matter in evolving proto-neutron stars by deepening the gravitational potential while halos cool it, providing a diagnostic distinct from hyperons.
A small vacuum-like dark-energy admixture in neutron stars with 400 MeV–1 GeV fermionic dark matter shrinks halo-induced radius differences from several kilometers to sub-kilometer scales and mass differences to ≲1%.
The study examines the effects of hyperons and H-dibaryons on f-mode oscillations in neutron stars using the quark meson coupling model and tests universal relations in the Cowling approximation.
The Lee-Huang-Yang beyond-mean-field correction measurably reduces the dimensionless moment of inertia of slowly rotating BEC dark stars at fixed compactness while preserving the I-Love universal relation to within a few percent.
Including hyperons reduces maximum neutron-star mass by 0.05-0.10 solar masses and increases radius at 1.4 solar masses by 0.5-0.8 km across all models while keeping every equation of state consistent with the 2-solar-mass limit.
citing papers explorer
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Causality alone bounds the maximum radius difference between different-mass neutron stars
Causality anchored to χEFT at low density implies the closed-form bound R(2.0 M_⊙) ≤ 1.16 R(1.4 M_⊙) − 1.1 km for neutron stars sharing one causal EoS, saturated by an analytic one-parameter family.
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Minimal Proton-Mass Dark Matter
A minimal dark matter model with one complex scalar carrying B and L numbers, stabilized by proton stability, with mass near the proton mass and relic density from UV freeze-in.
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Symmetry Energy Expansion with Strange Dense Matter
A redefinition of the symmetry energy expansion that incorporates finite strangeness consistent with SU(3) flavor symmetry and remains valid beyond typical neutron-star central densities.
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$\Lambda$ hyperons in core-collapse supernovae: Equilibration and neutrino opacities
Lambda hyperons equilibrate rapidly in post-collapse proto-neutron stars through nonleptonic NN to N Lambda processes and enhance low-energy muon neutrino opacities beyond nucleonic contributions.
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Systematic study of the morphology and length of slow stable hybrid star branches
Slow hadron-quark conversion in hybrid neutron stars creates extended stable 'waterfall' branches, reviving stiff hadronic equations of state that rapid-conversion analyses reject.
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Amortized Simulation-Based Inference of Relativistic Mean-Field Couplings for Neutron-Star Equations of State
Amortized neural posterior estimation reproduces nested sampling constraints on RMF couplings for neutron-star EOS with no bias and generates 30,000 samples in 2.5 seconds.
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Scalar diquarks in the QCD vacuum
A first-principles FRG approach to two-flavor QCD derives low-energy constants for the pion, sigma-meson and scalar diquark without parameters beyond QCD itself, including new diquark properties for color-superconducting models.
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Is the coexistence of strange quark stars and hadronic stars favored by astrophysical data? A Bayesian analysis
Bayesian analysis of astrophysical and laboratory data favors the two-families scenario of coexisting hadronic and strange quark stars over the one-family scenario.
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Neutron stars in a conservative $f(R,T)$ gravity
A conservative f(R,T) gravity reformulation decouples the gravitational sector from the microphysical equation of state, enabling computation of neutron star mass-radius relations and tidal deformabilities that satisfy current astrophysical constraints.
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A Physics Informed Bayesian Neural Network for the Neutron Star Equation of State
A physics-informed Bayesian neural network learns neutron-star equations of state from theoretical priors and constraints, then generates posterior mass-radius and mass-tidal-deformability distributions consistent with NICER radii and 2-solar-mass limits.
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Axial Oscillations of Viscous Neutron Stars
Causal viscous relativistic hydrodynamics applied to neutron stars yields new axial mode families without perfect-fluid counterparts, including mode avoidance and long-lived modes.
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Quark and hybrid stars with renormalization group improvement of NNLO perturbative QCD
RGOPT-resummed NNLO pQCD EoS for massive quarks in beta equilibrium is fitted and applied to construct pure quark stars (X=3.08-3.58) and hybrid stars (X~2-2.98) compatible with PSR J0740+6620 and GW190814.
-
Magnetic field dynamics in isolated neutron stars with an external dipole field
Long-term numerical-relativity runs find isolated neutron stars with an external dipole relax to a stable mixed poloidal-toroidal field with toroidal energy ≲10% after Tayler saturation.
-
Bayesian analysis of density profile of light dark matter elucidating the properties of dark matter admixed neutron stars in the presence of hyperons
Bayesian analysis finds that the likely ranges of light dark-matter fermion mass and exponential density-profile parameter in hyperon-containing neutron stars are nearly independent of the hadronic model for symmetry-energy slopes between 40 and 58 MeV, with HESS J1731-347 and GW170817 data playing,
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Nonradial oscillations of realistic anisotropic neutron stars: Axial modes
Axial modes of anisotropic neutron stars are integrated numerically for realistic EOS; frequency falls with mass, damping time rises, and scaled quantities follow a near-universal quadratic in compactness that is largely EOS-insensitive but mildly model-dependent.
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Modeling large glitches with core superfluidity in a Hybrid star
Hybrid star model with core quark pasta pinning superfluid vortices produces glitch amplitudes ΔΩ/Ω of order 10^{-6} matching Vela-like pulsar observations.
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Sensitivity of Neutron Star Observables to Transition Density in Hybrid Equation-of-State Models
Hybrid neutron-star equations of state remain sensitive to the low-density nucleonic model at transition densities around 2ρ₀, with model spread in radius and tidal deformability exceeding observational uncertainty by factors of ~1.8 and ~1.4.
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Neutron star with dark matter using vector portal
Vector-portal fermionic dark matter softens or stiffens the neutron-star equation of state depending on Z' mass, producing mass-radius and tidal-deformability signatures constrained by GW170817 and NICER.
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General gravitational properties of neutron stars: curvature invariants, binding energy, and trace anomaly
Roughly half of realistic neutron-star equations of state produce stars with negative Ricci scalar inside, and an improved analytic fit links gravitational mass M to baryonic mass Mb with maximum 3 percent variance.
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Dark Matter Heating in Evolving Proto-Neutron Stars: A Two-Fluid Approach
Dark matter cores heat baryonic matter in evolving proto-neutron stars by deepening the gravitational potential while halos cool it, providing a diagnostic distinct from hyperons.
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Sub-GeV dark matter in neutron stars: halo morphologies and their suppression by vacuum-like pressure
A small vacuum-like dark-energy admixture in neutron stars with 400 MeV–1 GeV fermionic dark matter shrinks halo-induced radius differences from several kilometers to sub-kilometer scales and mass differences to ≲1%.
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$f$-mode Oscillations for Hyperons and H-dibaryons in Neutron Stars
The study examines the effects of hyperons and H-dibaryons on f-mode oscillations in neutron stars using the quark meson coupling model and tests universal relations in the Cowling approximation.
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Slowly rotating condensate dark stars beyond the mean-field approximation
The Lee-Huang-Yang beyond-mean-field correction measurably reduces the dimensionless moment of inertia of slowly rotating BEC dark stars at fixed compactness while preserving the I-Love universal relation to within a few percent.
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Hyperonic equation of state for neutron stars: A systematic Bayesian comparison of density-dependent and non-linear relativistic mean-field models
Including hyperons reduces maximum neutron-star mass by 0.05-0.10 solar masses and increases radius at 1.4 solar masses by 0.5-0.8 km across all models while keeping every equation of state consistent with the 2-solar-mass limit.
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Sensitivity of the Neutron Star Equation of State Inferences to Mass and Radius Measurements
Theoretical inputs and the 2 solar mass lower limit dominate neutron star equation of state constraints across most densities, while radius data refines low densities and higher masses affect wider ranges.
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A Poincar\'e-covariant study of strange quark stars
A Poincaré-covariant vector-vector contact interaction yields an equation of state for strange quark matter whose mass-radius and tidal properties match pulsar and gravitational-wave constraints for two tuned parameter sets.
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Equation of State Extrapolation Systematics: Parametric vs. Nonparametric Inference of Neutron Star Structure
Nonparametric GP-based high-density extensions yield softer EOS posteriors with larger uncertainties than parametric PP extensions when jointly constrained by multi-messenger neutron star observations.
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Inferring neutron star properties through gravitational waves from r-modes and their relativistic counterparts
Two inference frameworks are developed for neutron star properties from r-mode gravitational waves, one assuming electromagnetic distance and the other estimating distance via universal relations plus an assumed equation of state, with Fisher-matrix error estimates.
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Radial oscillations of quark stars in light of current astrophysical constraints: A comparative study
Comparative numerical study of radial modes in strange quark stars using CFL, interacting, and linear causal EOS shows all satisfy current mass-radius bounds and produce 4-7 kHz fundamental frequencies.
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Spin effects in superfluidity, neutron matter and neutron stars
A review of spin effects, superfluidity, and magnetic fields in neutron matter and their influence on neutron-star structure, superfluid phases, and rotational dynamics.