How Well Do We Know the Neutron-Matter Equation of State at the Densities Inside Neutron Stars? A Bayesian Approach with Correlated Uncertainties

Singlet S-wave superfluidity of dilute neutron matter in the inner crust of neutron stars is studied within the correlated BCS (Bardeen, Cooper, Schrieffer) method, taking into account both pairing and short-range correlations. First, the equation of state (EOS) of normal neutron matter is calculated within the correlated-basis-function (CBF) method in lowest cluster order using the Argonne V18 and V4′ potentials and Jastrow-type correlation functions. The 1S0 superfluid gap is then calculated with these potentials and correlation functions. The dependence of our results on the choice of the correlation functions is ana- lyzed and the role of higher-order cluster corrections is considered. The values obtained for the 1S0 gap within this simplified scheme are comparable to those from other, more elaborate, methods.

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The I-Love-Q Relations for Superfluid Neutron Stars

Universe ◽

10.3390/universe7040111 ◽

2021 ◽

Vol 7 (4) ◽

pp. 111

Author(s):

Cheung-Hei Yeung ◽

Lap-Ming Lin ◽

Nils Andersson ◽

Greg Comer

Keyword(s):

Fluid Dynamics ◽

Equation Of State ◽

Neutron Stars ◽

Quadrupole Moment ◽

Fluid Model ◽

Normal Component ◽

Approximate Equation ◽

Mean Field Model ◽

Polytropic Model ◽

Two Fluid

The I-Love-Q relations are approximate equation-of-state independent relations that connect the moment of inertia, the spin-induced quadrupole moment, and the tidal deformability of neutron stars. In this paper, we study the I-Love-Q relations for superfluid neutron stars for a general relativistic two-fluid model: one fluid being the neutron superfluid and the other a conglomerate of all charged components. We study to what extent the two-fluid dynamics might affect the robustness of the I-Love-Q relations by using a simple two-component polytropic model and a relativistic mean field model with entrainment for the equation-of-state. Our results depend crucially on the spin ratio Ωn/Ωp between the angular velocities of the neutron superfluid and the normal component. We find that the I-Love-Q relations can still be satisfied to high accuracy for superfluid neutron stars as long as the two fluids are nearly co-rotating Ωn/Ωp≈1. However, the deviations from the I-Love-Q relations increase as the spin ratio deviates from unity. In particular, the deviation of the Q-Love relation can be as large as O(10%) if Ωn/Ωp differ from unity by a few tens of percent. As Ωn/Ωp≈1 is expected for realistic neutron stars, our results suggest that the two-fluid dynamics should not affect the accuracy of any gravitational waveform models for neutron star binaries that employ the relation to connect the spin-induced quadrupole moment and the tidal deformability.

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Constraining the equation of state of dense nuclear matter using thermal emission of neutron stars

Journal of Physics Conference Series ◽

10.1088/1742-6596/1667/1/012001 ◽

2020 ◽

Vol 1667 ◽

pp. 012001

Author(s):

Nicolas Baillot d’Étivaux ◽

Jérôme Margueron ◽

Sebastien Guillot ◽

Natalie Webb ◽

Màrcio Catelan ◽

...

Keyword(s):

Equation Of State ◽

Neutron Stars ◽

Nuclear Matter ◽

Thermal Emission ◽

Dense Nuclear Matter

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Ferromagnetism in neutron matter and its implication for the neutron star equation of state

10.1063/1.3629525 ◽

2011 ◽

Author(s):

J. P. W. Diener ◽

F. G. Scholtz ◽

Ersin Göğüş ◽

Ünal Ertan ◽

Tomaso Belloni

Keyword(s):

Neutron Star ◽

Equation Of State ◽

Neutron Matter

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Nuclear equation of state and neutron star cooling

International Journal of Modern Physics E ◽

10.1142/s021830131750015x ◽

2017 ◽

Vol 26 (04) ◽

pp. 1750015 ◽

Cited By ~ 14

Author(s):

Yeunhwan Lim ◽

Chang Ho Hyun ◽

Chang-Hwan Lee

Keyword(s):

Neutron Star ◽

Equation Of State ◽

Neutron Stars ◽

Nuclear Matter ◽

Thermal Evolution ◽

Observation Data ◽

Nuclear Equation Of State ◽

The Core ◽

Dense Nuclear Matter ◽

Nuclear Models

In this paper, we investigate the cooling of neutron stars with relativistic and nonrelativistic models of dense nuclear matter. We focus on the effects of uncertainties originated from the nuclear models, the composition of elements in the envelope region, and the formation of superfluidity in the core and the crust of neutron stars. Discovery of [Formula: see text] neutron stars PSR J1614−2230 and PSR J0343[Formula: see text]0432 has triggered the revival of stiff nuclear equation of state at high densities. In the meantime, observation of a neutron star in Cassiopeia A for more than 10 years has provided us with very accurate data for the thermal evolution of neutron stars. Both mass and temperature of neutron stars depend critically on the equation of state of nuclear matter, so we first search for nuclear models that satisfy the constraints from mass and temperature simultaneously within a reasonable range. With selected models, we explore the effects of element composition in the envelope region, and the existence of superfluidity in the core and the crust of neutron stars. Due to uncertainty in the composition of particles in the envelope region, we obtain a range of cooling curves that can cover substantial region of observation data.

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Pulsars in Globular Clusters

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308015810 ◽

2007 ◽

Vol 3 (S246) ◽

pp. 291-300 ◽

Cited By ~ 7

Author(s):

Scott M. Ransom

Keyword(s):

Equation Of State ◽

Neutron Stars ◽

Globular Clusters ◽

Main Sequence ◽

Galactic Disk ◽

Nuclear Density ◽

Millisecond Pulsars ◽

Eccentric Orbits ◽

The Masses ◽

Current Record

AbstractGlobular clusters produce orders of magnitude more millisecond pulsars per unit mass than the Galactic disk. Since the first cluster pulsar was uncovered 20 years ago, at least 138 have been identified – most of which are binary millisecond pulsars. Because their origins involve stellar encounters, many of the systems are exotic objects that would never be observed in the Galactic disk. Examples include pulsar-main sequence binaries, extremely rapid rotators (including the current record holder), and millisecond pulsars in highly eccentric orbits. These systems are allowing new probes of the interstellar medium, the equation of state of material at supra-nuclear density, the masses of neutron stars, and globular cluster dynamics.

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