Mirror dark matter admixture via mutual mean-field shifts softens the nuclear EOS, raises central densities, lowers maximum masses, and moves the direct Urca onset to higher or lower masses depending on symmetry-energy stiffness.
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The Radius of PSR J0740+6620 from NICER and XMM-Newton Data
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abstract
PSR J0740$+$6620 has a gravitational mass of $2.08\pm 0.07~M_\odot$, which is the highest reliably determined mass of any neutron star. As a result, a measurement of its radius will provide unique insight into the properties of neutron star core matter at high densities. Here we report a radius measurement based on fits of rotating hot spot patterns to Neutron Star Interior Composition Explorer (NICER) and X-ray Multi-Mirror (XMM-Newton) X-ray observations. We find that the equatorial circumferential radius of PSR J0740$+$6620 is $13.7^{+2.6}_{-1.5}$ km (68%). We apply our measurement, combined with the previous NICER mass and radius measurement of PSR J0030$+$0451, the masses of two other $\sim 2~M_\odot$ pulsars, and the tidal deformability constraints from two gravitational wave events, to three different frameworks for equation of state modeling, and find consistent results at $\sim 1.5-3$ times nuclear saturation density. For a given framework, when all measurements are included the radius of a $1.4~M_\odot$ neutron star is known to $\pm 4$% (68% credibility) and the radius of a $2.08~M_\odot$ neutron star is known to $\pm 5$%. The full radius range that spans the $\pm 1\sigma$ credible intervals of all the radius estimates in the three frameworks is $12.45\pm 0.65$ km for a $1.4~M_\odot$ neutron star and $12.35\pm 0.75$ km for a $2.08~M_\odot$ neutron star.
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representative citing papers
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.
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.
Hybrid stars with a 2SC+⟨dd⟩ quark core cool hotter than with 2SC and near CFL; with a 3P2 gap near 5×10^8 K their cooling curves pass through the observed temperatures of 3C58, Vela Jr., and Vela-like pulsars.
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.
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.
Causal viscous relativistic hydrodynamics applied to neutron stars yields new axial mode families without perfect-fluid counterparts, including mode avoidance and long-lived modes.
Emulator-assisted Bayesian inference of an extended Skyrme EDF, jointly constrained by nuclear observables, ab initio calculations, and NICER data, produces posteriors yielding consistent neutron star crust and core properties with a provided multivariate Gaussian for bulk nuclear matter parameters.
New quasi-universal relations connect static tidal deformability Λ⁰ to its dynamical correction Λ² and to Mω* with equation-of-state scatter below 5% and 2.8% respectively across 59 models.
Bayesian NS EoS study using full nuclear posterior distributions and consistent crust modeling finds increased surface thickness and crustal moment of inertia relative to prior work.
A new relativistic model for accretion-powered X-ray pulsars enables simultaneous computation of phase-averaged spectra and pulse profiles, applied to NuSTAR data for Her X-1 to extract physical parameters and beaming patterns.
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.
Mass-gap compact objects could be hybrid stars only with very early deconfinement and stiff quark matter; confirming 1.4 M⊙ twin stars would cap hybrid-star maximum mass below 2.2 M⊙.
Joint NICER+IXPE pulse-profile modeling of SRGA J144459.2-604207 favors large neutron-star mass and radius with two independent hotspots but shows strong sensitivity to joint-analysis methodology.
NLED alters photon propagation near magnetars, producing ~10% errors in inferred radii via ray-tracing and a minimal ~350 ns travel-time delay.
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.
citing papers explorer
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A self-consistent single-fluid framework for neutron stars admixed with mirror dark matter
Mirror dark matter admixture via mutual mean-field shifts softens the nuclear EOS, raises central densities, lowers maximum masses, and moves the direct Urca onset to higher or lower masses depending on symmetry-energy stiffness.
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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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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.
-
Cooling of Hybrid Stars with a 2SC+$<dd>$ Phase
Hybrid stars with a 2SC+⟨dd⟩ quark core cool hotter than with 2SC and near CFL; with a 3P2 gap near 5×10^8 K their cooling curves pass through the observed temperatures of 3C58, Vela Jr., and Vela-like pulsars.
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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.
-
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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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.
-
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.
-
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.
-
Emulator-Assisted Nuclear DFT Inference and Its Consequences for the Structure of Neutron Stars
Emulator-assisted Bayesian inference of an extended Skyrme EDF, jointly constrained by nuclear observables, ab initio calculations, and NICER data, produces posteriors yielding consistent neutron star crust and core properties with a provided multivariate Gaussian for bulk nuclear matter parameters.
-
Universal Relations with Dynamical Tides
New quasi-universal relations connect static tidal deformability Λ⁰ to its dynamical correction Λ² and to Mω* with equation-of-state scatter below 5% and 2.8% respectively across 59 models.
-
Properties of the neutron star crust informed by nuclear structure data
Bayesian NS EoS study using full nuclear posterior distributions and consistent crust modeling finds increased surface thickness and crustal moment of inertia relative to prior work.
-
A New Relativistic Model for Spectral Formation in Accretion-Powered X-ray Pulsars: Pulse Profiles and Phase-Averaged Spectra
A new relativistic model for accretion-powered X-ray pulsars enables simultaneous computation of phase-averaged spectra and pulse profiles, applied to NuSTAR data for Her X-1 to extract physical parameters and beaming patterns.
-
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.
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Hybrid stars among mass gap objects are excluded by twin stars at $1.4\,M_\odot$
Mass-gap compact objects could be hybrid stars only with very early deconfinement and stiff quark matter; confirming 1.4 M⊙ twin stars would cap hybrid-star maximum mass below 2.2 M⊙.
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Pulse profile modelling of the 2024 outburst of the accreting millisecond pulsar SRGA J144459.2-604207
Joint NICER+IXPE pulse-profile modeling of SRGA J144459.2-604207 favors large neutron-star mass and radius with two independent hotspots but shows strong sensitivity to joint-analysis methodology.
-
Nonlinear electrodynamics in magnetars: systematic effects on radius constraints and timing analysis
NLED alters photon propagation near magnetars, producing ~10% errors in inferred radii via ray-tracing and a minimal ~350 ns travel-time delay.
-
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,
-
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.
-
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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Properties of Stable Massive Quark Stars in Holography
Holographic model of massive deconfined quarks yields a stiff enough equation of state to allow stable 2-solar-mass hybrid stars with quark cores for certain nuclear phases.
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Rotational effects in quark stars: comparing different models
Rotation amplifies differences between the vector MIT bag and DDQM equations of state for quark stars, with MIT supporting more massive stars and a full decomposition of gravitational, internal, rotational, and binding energies provided.
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Tracing the Trace Anomaly of Dense Matter inside Neutron Stars
Quasi-universal relations connect the trace anomaly profile of neutron star matter to stellar compactness, moment of inertia, and tidal deformability, yielding a central value estimate of Δ_c = 0.1770^{+0.0365}_{-0.0432} for a 1.4 M_⊙ star.
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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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Hybrid stars with hyperons: structure based on QCD sum rule coupling constants
Hybrid star EOS constructed from QCDSR couplings in RMF hadronic model and bag/NJL quark models with Gibbs/Maxwell transitions yields mass-radius and tidal deformability predictions.
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Bayesian analysis of the shear modulus in the neutron-star crust
Bayesian modeling with informed priors reduces uncertainties in neutron-star crust shear properties, predicting torsional mode frequencies of 20-50 Hz compatible with observations.
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Core Composition Effects on the QCD Axion Mass Limit from Neutron Star Cooling
Varying neutron star core composition with hyperons and Delta resonances mildly affects the QCD axion mass limit from cooling, potentially bringing the DFSZ limit into the IAXO sensitivity window.
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Quark Stars in Ricci-Determinant Gravity with an Interacting Quark Equation of State
Quark stars in Ricci-Determinant gravity with interacting quark EoS exhibit lower compactness than in GR and become unstable at high central densities when perturbative gravity terms exceed about half the GR contribution.
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Impact of the equation of state on core collapse supernovae I: the low-$T/|W|$ instability
Simulations show the low-T/|W| instability develops robustly across five nuclear EOS in a rapidly rotating 35 M⊙ progenitor, with dominant GW frequency correlating to PNS compactness and stiffness.
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Characterizing the quark-hadron mixed phase in compact star cores : sensitivity to nuclear saturation and quark-model parameters at finite-temperature
The quark-hadron mixed phase width in hybrid stars is mainly controlled by effective nucleon mass and symmetry energy, with temperature reducing the width and softening the EOS while strong vector repulsion is needed to match massive pulsar and NICER data.
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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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Buchdahl Limit and TOV Equations in Interacting Vacuum Scenarios
Interacting vacuum energy relaxes the pressure gradient inside stars, allowing finite central pressure and compactness beyond the Buchdahl bound for suitable coupling strengths.
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Impact of Anisotropy on Neutron Star Structure and Curvature
Moderate positive pressure anisotropy raises neutron star maximum mass to about 2.4 solar masses and compactness by up to 20 percent, with curvature scalars tied to matter showing strong sensitivity while the Weyl scalar stays largely insensitive.
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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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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.
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Nuclear Physics of Binary Neutron Star Mergers
Review summarizing the role of dense-matter equation of state, weak interactions, and r-process nucleosynthesis in binary neutron star mergers and their multimessenger observables.
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Core-collapse supernovae and supernova neutrinos
A review chapter sketching the neutrino-driven mechanism for core-collapse supernovae, the importance of nuclear physics inputs, and multi-messenger signals.