Viscous neutron stars have new families of axial oscillation modes without perfect-fluid counterparts, featuring mode avoidance and long-lived modes.
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PSR J0030+0451 Mass and Radius from NICER Data and Implications for the Properties of Neutron Star Matter
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abstract
Neutron stars are not only of astrophysical interest, but are also of great interest to nuclear physicists, because their attributes can be used to determine the properties of the dense matter in their cores. One of the most informative approaches for determining the equation of state of this dense matter is to measure both a star's equatorial circumferential radius $R_e$ and its gravitational mass $M$. Here we report estimates of the mass and radius of the isolated 205.53 Hz millisecond pulsar PSR J0030+0451 obtained using a Bayesian inference approach to analyze its energy-dependent thermal X-ray waveform, which was observed using the Neutron Star Interior Composition Explorer (NICER). This approach is thought to be less subject to systematic errors than other approaches for estimating neutron star radii. We explored a variety of emission patterns on the stellar surface. Our best-fit model has three oval, uniform-temperature emitting spots and provides an excellent description of the pulse waveform observed using NICER. The radius and mass estimates given by this model are $R_e = 13.02^{+1.24}_{-1.06}$ km and $M = 1.44^{+0.15}_{-0.14}\ M_\odot$ (68%). The independent analysis reported in the companion paper by Riley et al. (2019) explores different emitting spot models, but finds spot shapes and locations and estimates of $R_e$ and $M$ that are consistent with those found in this work. We show that our measurements of $R_e$ and $M$ for PSR J0030$+$0451 improve the astrophysical constraints on the equation of state of cold, catalyzed matter above nuclear saturation density.
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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.
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.
A renormalization-group invariant mean-field treatment of the Parity-Doublet Model is developed that consistently includes baryonic vacuum fluctuations and is used to study chiral symmetry restoration in two-flavor nuclear and neutron-star matter for chosen values of the chirally invariant mass m0.
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 show mass-scaled frequency and damping time with nearly universal quadratic dependence on compactness, insensitive to EOS and anisotropy model.
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 admixed in neutron stars produces mediator-mass-dependent changes to the equation of state, yielding distinct mass-radius relations and tidal deformabilities that observations can use to constrain the model.
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.
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.
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.
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 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.
Conformalized quantile regression applied post hoc to neutron star posterior samples yields reliable uncertainty bands validated by empirical coverage studies.
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.
Interacting vacuum energy relaxes the pressure gradient inside stars, allowing finite central pressure and compactness beyond the Buchdahl bound for suitable coupling strengths.
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.
A review of spin effects, superfluidity, and magnetic fields in neutron matter and their influence on neutron-star structure, superfluid phases, and rotational dynamics.
citing papers explorer
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Axial Oscillations of Viscous Neutron Stars
Viscous neutron stars have new families of axial oscillation modes without perfect-fluid counterparts, featuring mode avoidance and long-lived modes.
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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.
-
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.
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Renormalization-Group Invariant Parity-Doublet Model for Nuclear and Neutron-Star Matter
A renormalization-group invariant mean-field treatment of the Parity-Doublet Model is developed that consistently includes baryonic vacuum fluctuations and is used to study chiral symmetry restoration in two-flavor nuclear and neutron-star matter for chosen values of the chirally invariant mass m0.
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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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On the non-radial oscillations of realistic anisotropic neutron stars: Axial modes
Axial modes of anisotropic neutron stars show mass-scaled frequency and damping time with nearly universal quadratic dependence on compactness, insensitive to EOS and anisotropy model.
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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 admixed in neutron stars produces mediator-mass-dependent changes to the equation of state, yielding distinct mass-radius relations and tidal deformabilities that observations can use to constrain the model.
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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.
-
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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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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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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Conformal prediction for uncertainties in the neutron star equation of state
Conformalized quantile regression applied post hoc to neutron star posterior samples yields reliable uncertainty bands validated by empirical coverage studies.
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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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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.
- General-relativistic resistive-magnetohydrodynamics simulations of self-consistent magnetized rotating neutron stars