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neutron stars including the effects of chaotic magnetic fields and anomalous magnetic moments

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Chinese Physics C 2017年第4期41卷 117-123页

作者：吴飞吴琛任中洲 Physics Department Nanjing University Shanghai Institute of Applied Physics Chinese Academy of Science Center of Theoretical Nuclear Physics National Laboratory of Heavy-Ion Accelerator Kavli Institute for Theoretical Physics China Chinese Academy of Sciences

The relativistic mean field（RMF） FSUGold model extended to include hyperons is employed to study the properties of neutron stars with strong magnetic fields.The chaotic magnetic field approximation is utilized.The effect of anomalous magnetic moments（AMMs） is also investigated.It is shown that the equation of state（EOS）of neutron star matter is stiffened by the presence of the magnetic field,which increases the maximum mass of a neutron star by around 6%.The AMMs only have a small influence on the EOS of neutron star matter,and increase the maximum mass of a neutron star by 0.02M（sun）.Neutral particles are spin polarized due to the presence of the AMMs.

关键词： magnetic field neutron stars equation of state

Systematic comparison of initial velocities for neutron stars in different models

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Research in Astronomy and Astrophysics 2016年第7期16卷 1-8页

作者： Ali Taani Applied Science Department Aqaba University College Aqaba Al-Balqa' Applied University RO. Box 1199 77110Salt Jordan Department of Applied Physics and Astronomy University of Sharjah P.O. Box 27272 Sharjah United Arab Emirates

I have studied the initial velocity（Maxwellian and exponential distributions） and the scale height of isolated old（aged≥10^9yr） neutron stars（NSs） at different Galactocentric distances R in three population models. The smooth time-independent 3-D axisymmetric gravitational potentials（MiyamotoNagai and Paczy n′ski models） were also used. The correlation between these quantities significantly affects the shapes of the profiles and distributions of the simulated sample, because the differences in the initial kick can arise from differences in the formation and evolution of NSs with other physical parameters. The scale height of the density distribution increases systematically with R. I have also shown that the distribution of old NSs in these population models agrees with the observed structure of the Galaxy in terms of initial velocities（1-D and 3-D）, as well as the scale height distributions. These distributions tend to have an asymptotic behavior at the point R = 2.75 kpc. This means that the quality of the models can be described in terms of a mean of the fitted Gaussian, and this could also give an overall perspective of the phase space properties of nearby old NSs on a given gravitational potential.

关键词： pulsar general stars neutron stars statistics stars evolution Galaxy structure Galaxy disk galaxies kinematics and dynamics

Influence of the nuclear equation of state on the hadron-quark phase transition in neutron stars

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Chinese Physics C 2008年第7期32卷 536-542页

作者：杨芳申虹 Department of Physics Nankai UniversityTianjin 300071China

We study the hadron-quark phase transition in the interior of neutron stars, and examine the influence of the nuclear equation of state on the phase transition and neutron star properties. The relativistic mean field theory with several parameter sets is used to construct the nuclear equation of state, while the Nambu-Jona-Lasinio model is used for the description of the deconfined quark phase. Our results show that a harder nuclear equation of state leads to an earlier onset of a mixed phase of hadronic and quark matter. We find that a massive neutron star possesses a mixed phase core, but it is not dense enough to possess a pure quark core.

关键词： hadron-quark phase transition equation of state neutron stars

Dependence of the tidal deformability of neutron stars on the nuclear equation of state

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Chinese Physics C 2023年第1期47卷 160-167页

作者：谢文杰陈建玲马紫微郭俊华祝龙 Department of Physics Yuncheng UniversityYuncheng 044000China Sino-French Institute of Nuclear Engineering and Technology Sun Yat-sen UniversityZhuhai 519082China

Within the Bayesian framework,using an explicitly isospin-dependent parametric equation of state(EOS)for the core of neutron stars(NSs),we studied how the NS EOS behaves when we confront it with the tidal deformabilitiesΛ1.4abilities of massive NSs.We found that it does not significantly improve the constraints on the NS EOS but has a weak effect on narrowing down the slope parameter of the symmetry energy by decreasing the measurement errors ofΛ1.4.Both the isospin-dependent and isospin-independent parts of the NS EOS were significantly constrained and raised as the tidal deformabilities of massive NSs were adopted in the calculations,especially in high-density regions.We also found thatΛ1.4symmetry energy,whereas the opposite occurs for the radius of canonical NSs R1.4.The tidal deformability of an NS with two times the solar massΛ2.0ergy,andΛ1.4and R1.4have no correlation with the former.

关键词： symmetry energy equation of state tidal deformability Bayesian inference approach neutron stars

Crust-core properties of neutron stars in the Nambu–Jona-Lasinio model

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Chinese Physics C 2018年第5期42卷 70-78页

作者：韦斯纳杨荣瑶蒋维洲 School of Physics Southeast UniversityNanjing 211189China

We adopt the Nambu–Jona-Lasinio(NJL) model to study the crust-core transition properties in neutron stars(NSs). For a given momentum cutoff and symmetry energy of saturation density in the NJL model, decreasing the slope of the symmetry energy gives rise to an increase in the crust-core transition density and transition pressure.Given the slope of the symmetry energy at saturation density, the transition density and corresponding transition pressure increase with increasing symmetry energy. The increasing trend between the fraction of the crustal moment of inertia and the slope of symmetry energy at saturation density indicates that a relatively large momentum cutoff of the NJL model is preferred. For a momentum cutoff of 500 Me V, the fraction of the crustal moment of inertia clearly increases with the slope of symmetry energy at saturation density. Thus, at the required fraction(7%) of the crustal moment of inertia, the NJL model with momentum cutoff of 500 Me V and a large slope of the symmetry energy of saturation density can give the upper limit of the mass of the Vela pulsar to be above 1.40 M.

关键词： neutron stars Nambu-Jona-Lasinio model glitches crust-core transition

The spatial distribution of old neutron stars in the Galaxy

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Science China(Physics,Mechanics & Astronomy) 2010年第10期53卷 1939-1946页

作者： WEI YingChun ZHANG ChengMin WU XinJi ZHAO YongHeng CHOU ChiKang LUO ALi National Astronomical Observatories Chinese Academy of SciencesBeijing 100012China Department of Astronomy Peking UniversityBeijing 100871China National Astronomical Observatories/Urumqi Observatory Chinese Academy of SciencesUrumqi 830011China

The spatial distributions of old neutron stars (NSs) with ages 109 to 1010 yr in our Galaxy are investigated by Monte Carlo simulation under two different initial random velocity models.It is found that the scale heights of the distribution increase with the Galactic radial distance.The location of the peak of the NS distribution is closer to the Galactic center than that of their progenitors.The results from our detailed numerical analysis reveal that there is resemblance between the simulated old NS distribution and the structure of the observed HI disk.

关键词： neutron stars Galaxy structure Galaxy disk star evolution

Effects of the density dependence of the symmetry energy on neutron stars

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Chinese Physics C 2010年第11期34卷 1709-1713页

作者：刘晓进吴琛任中洲 Physics Department Nanjing University Center of Theoretical Nuclear Physics National Laboratory of Heavy Ion Accelerator

In this paper,we include the density dependence behavior of the symmetry energy in the improved quark mass density dependent （IQMDD） model.Under the mean field approximation,this model is applied to investigate neutron star matter and neutron stars successfully.Effects of the density dependence of the symmetry energy on neutron stars are described.

关键词： symmetry energy neutron stars relativistic mean field approximation quark-meson coupling

The EOSs and the Blatant Discrepancy in Modelling Massive neutron stars: Origin and a Possible Solution Method

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现代物理(英文) 2023年第11期14卷 1458-1463页

作者： Ahmad A. Hujeirat Mauritz M. Wicker IWR University of Heidelberg Heidelberg Germany

Exploring the state of ultra-cold supranuclear dense matter that makes up the cores of massive neutron stars is one of the greatest unresolved problems in modern physics. In this letter, we show that when the interiors of pulsars are made of compressible and dissipative normal matter, the commonly used solution procedures combined with the known EOSs yield widely scattered solutions and poorly determined radii. A remarkable agreement emerges, however, if pulsars harbour cores that are made of incompressible entropy-free superfluids (SuSu-matter) embedded in flat spacetimes. Such supranuclear dense matter should condensate to form false vacua as predicated by non-perterbative QCD vacuum. The solutions here are found to be physically consistent and mathematically elegant, irrespective of the object’s mass. Based thereon, we conclude that the true masses of massive NSs may differ significantly from those revealed by direct observation.

关键词： General Relativity Pulsars neutron stars EOSs QCD Incompressibility Superfluidity Super-Conductivity

Cooling of Akmal-Pandharipande-Ravenhall neutron stars with a rotochemical heating source

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Chinese Physics C 2010年第12期34卷 1818-1822页

作者：皮春梅杨书华周霞周爱芝 Institute of Astrophysics Huazhong Normal University Department of Physics and Electronics Hubei University of Education Urumqi Observatory NAOC CAS

Employing phenomenological density-dependent critical temperatures of strong singlet-state proton pairing and of moderate triplet-state neutron pairing, we investigate the effects of rotochemical heating on the thermal evolution of superfluid neutron stars whose cores consist of npe matter with the Akmal-Pandharipande-Ravenhall equation of state. Since the star is not quite in the weak interaction equilibrium state during spin-down, the departure from the chemical equilibrium leads to the rotochemical heating in a rotating NS which will increase the stellar＇s temperature. Our calculations show that the rotochemical heating delays the cooling of superfluid neutron stars considerably and makes the previous classification of NS cooling ambiguous. What＇s more, our model is currently consistent with all the observational data, and in particular some middle-aged and cold NSs （PRS J0205＋6449 in 3C 58, PRS J1357-6429, RX J007.0＋7303 in CTA 1, Vela） can be better explained when taking into account rotochemical heating.

关键词： neutron stars thermal evolution rotation rotochemical heating superfluidity