RELATIVISTIC URCA PROCESSES IN NEUTRON STARS WITH AN ANTIKAON CONDESATE

2011 ◽  
Vol 20 (supp02) ◽  
pp. 146-151 ◽  
Author(s):  
MOISÉS RAZEIRA ◽  
ALEXANDRE MESQUITA ◽  
CÉSAR A. Z. VASCONCELLOS ◽  
ROSANA O. GOMES ◽  
AURORA PÉREZ MARTÍNEZ ◽  
...  
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Nuclear Matter ◽  
Degrees Of Freedom ◽  
Critical Density ◽  
Heat Radiation ◽  
Critical Threshold ◽  
Neutron Star Matter ◽  
Isospin Asymmetry ◽  
Urca Process

A recently developed effective relativistic theory for nuclear matter is applied to the description of the cooling process of baryon degenerate neutron star matter through neutrino emission considering direct URCA processes. In our approach nucleons and antikaon condensates interact with σ, ω, ρ, δ and ς meson fields. Our results indicate a substantial decrease of the critical threshold density for the URCA process. This is because the presence of these interacting degrees of freedom increase the proportion of protons, producing simultaneously the reduction of the isospin asymmetry in nuclear matter. Our results also indicate that neutron stars with larger masses than MNE ~ 0.9M⊙, which represents the stellar critical threshold (the mass of the neutron star whose baryon central density reached the critical density) would be cooled efficiently and be outside the possibility of observation by heat radiation in a few years.

EFFECTS OF IN-MEDIUM MODIFICATION OF WEAKLY INTERACTING LIGHT BOSON MASS IN NEUTRON STARS

2011 ◽  
Vol 26 (05) ◽  
pp. 367-375 ◽  
Author(s):  
A. SULAKSONO ◽  
MARLIANA ◽  
KASMUDIN
Keyword(s):  
Neutron Star ◽  
Binding Energy ◽  
Neutron Stars ◽  
Nuclear Matter ◽  
Observational Data ◽  
Boson Mass ◽  
Characteristic Scale ◽  
Neutron Star Matter ◽  
Weakly Interacting ◽  
Medium Modification

The effects of the presence of weakly interacting light boson (WILB) in neutron star matter have been revisited. Direct checking based on the experimental range of symmetric nuclear matter binding energy1 and the fact that the presence of this boson should give no observed effect on the crust properties of neutron star matter, shows that the characteristic scale of WILB [Formula: see text] should be ≤2 GeV-2. The recent observational data with significant low neutron stars radii2 and the recent largest pulsar which has been precisely measured, i.e. J1903+0327 (Ref. 3) indicate that in-medium modification of WILB mass in neutron stars cannot be neglected.

NEUTRON STARS WITH KAON CONDENSATION IN RELATIVISTIC EFFECTIVE MODEL

2013 ◽  
Vol 22 (05) ◽  
pp. 1350026 ◽  
Author(s):  
CHEN WU ◽  
WEI-LIANG QIAN ◽  
YU-GANG MA ◽  
JI-FENG YANG
Keyword(s):  
Field Theory ◽  
Neutron Star ◽  
Neutron Stars ◽  
Nuclear Matter ◽  
Optical Potential ◽  
Mean Field Theory ◽  
Mean Field ◽  
Neutron Star Matter ◽  
Relativistic Mean Field ◽  
Kaon Condensation

Relativistic mean-field theory with parameter sets FSUGold and IU-FSU is extended to study the properties of neutron star matter in β equilibrium by including Kaon condensation. The mixed phase of normal baryons and Kaon condensation cannot exist in neutron star matter for the FSUGold model and the IU-FSU model. In addition, it is found that when the optical potential of the K- in normal nuclear matter UK ≳ -100 MeV , the Kaon condensation phase is absent in the inner cores of the neutron stars.

scholarly journals Neutron Stars in the Symmetron Model

Universe ◽  
2021 ◽  
Vol 8 (1) ◽  
pp. 6
Author(s):  
Bernardo F. de Aguiar ◽  
Raissa F. P. Mendes ◽  
Felipe T. Falciano
Keyword(s):  
Dark Energy ◽  
Neutron Star ◽  
Solar System ◽  
Neutron Stars ◽  
Nuclear Matter ◽  
Degrees Of Freedom ◽  
Linear Coupling ◽  
Stability Properties ◽  
Energy Models ◽  
Opening Up

Screening mechanisms are often deployed by dark energy models to conceal the effects of their new degrees of freedom from the scrutiny of terrestrial and solar system experiments. However, the extreme properties of nuclear matter may lead to a partial failure of screening mechanisms inside the most massive neutron stars observed in nature, opening up the possibility of probing these theories with neutron star observations. In this work, we explore equilibrium and stability properties of neutron stars in two variants of the symmetron model. We show that around sufficiently compact neutron stars, the symmetron is amplified with respect to its background (cosmological) value by several orders of magnitude, and that the properties of such unscreened stars are sensitive to corrections to the leading linear coupling between the symmetron and matter.

scholarly journals Nuclear equation of state and neutron star cooling

2017 ◽  
Vol 26 (04) ◽  
pp. 1750015 ◽  
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.

scholarly journals Constraints on Microscopic and Phenomenological Equations of State of Dense Matter from GW170817

Universe ◽  
2019 ◽  
Vol 5 (10) ◽  
pp. 204 ◽  
Author(s):  
Domenico Logoteta ◽  
Ignazio Bombaci
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Equations Of State ◽  
Mean Field ◽  
Dense Matter ◽  
Neutron Star Matter ◽  
Field Approach ◽  
Relativistic Mean Field ◽  
Three Body ◽  
Good Agreement

We discuss the constraints on the equation of state (EOS) of neutron star matter obtained by the data analysis of the neutron star-neutron star merger in the event GW170807. To this scope, we consider two recent microscopic EOS models computed starting from two-body and three-body nuclear interactions derived using chiral perturbation theory. For comparison, we also use three representative phenomenological EOS models derived within the relativistic mean field approach. For each model, we determine the β -stable EOS and then the corresponding neutron star structure by solving the equations of hydrostatic equilibrium in general relativity. In addition, we calculate the tidal deformability parameters for the two neutron stars and discuss the results of our calculations in connection with the constraints obtained from the gravitational wave signal in GW170817. We find that the tidal deformabilities and radii for the binary’s component neutron stars in GW170817, calculated using a recent microscopic EOS model proposed by the present authors, are in very good agreement with those derived by gravitational waves data.

scholarly journals The Great Wall: Urca Cooling Layers in the Accreted NS Crust

2018 ◽  
Vol 178 ◽  
pp. 04004 ◽  
Author(s):  
Zach Meisel
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Beta Decay ◽  
Dense Matter ◽  
Thermal Barrier ◽  
Paper Briefly ◽  
The Past ◽  
Heating And Cooling ◽  
Urca Process ◽  
Great Wall

Accreting neutron stars host a number of astronomical observables which can be used to infer the properties of the underlying dense matter. These observables are sensitive to the heating and cooling processes taking place in the accreted neutron star (NS) crust. Within the past few years it has become apparent that electron-capture/beta-decay (urca) cycles can operate within the NS crust at high temperatures. Layers of nuclei undergoing urca cycling can create a thermal barrier, or Great Wall, between heating occurring deep in the crust and the regions above the urca layers. This paper briefly reviews the urca process and the implications for observables from accreting neutron stars.

Neutron Star Matter and Neutron Star Models

1974 ◽  
Vol 29 (6) ◽  
pp. 933-946
Author(s):  
H. Heintzmann ◽  
W. Hillebrandt ◽  
M. F. El Eid ◽  
E. R. Hilf
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
High Mass ◽  
Mass Limit ◽  
Neutron Star Matter ◽  
Density Region ◽  
Star Models ◽  
Boson Exchange ◽  
Realistic Interaction ◽  
General Relativistic

Various methods to study the ground state of neutron star matter are compared and the corresponding neutron star models are contrasted with each other. In the low density region ρ < 1014gr cm-3 the nuclear gas is treated here by means of a Thomas Fermi method and the nuclei are described by the droplet model of Myers and Swiatecki. For ρ > 1014 gr cm-3 both standard Brueckner theory with more realistic interaction (one-boson-exchange) potentials and the semiphenomenological theory of Fermi liquids (together with the standard Reid softcore potential) are applied to neutron star matter. It is shown that while the high mass limit of neutron stars is hardly affected, some properties of lowmass neutron stars such as their binding depend sensitively on these refinements. Various tentative (but unreliable) extensions of the equation of state into high density regime ρ > 1015 gr cm-3 are investigated and it is shown that the mass limit for heavy neutron stars lies around 2.5 solar masses. It is further shown that a third family of stable (hyperon) stars is not forbidden by general relativistic arguments if there is a phase transition at high densities.

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