中子星的热演化和磁衰减

本文研究了中子星的热演化、自转演化和磁场演化的相互影响．考虑了一个自洽模型：中子星因磁偶极辐射而自转减慢，在内部产生某些加热过程，中子星磁场通过壳层的欧姆耗散来衰减．结果表明，磁场衰减提高了加热过程的重要性；相反，加热效应减慢了磁衰减．因此可以得出，中子星的热、自转和磁场也许不是独立演化的．不仅如此，这些演化与初始条件有关，因此，人们也许可以从射电和Ｘ射线观测对脉冲星年龄、初始磁场和周期给出某些限制．     

Magnetic Fields of Neutron Stars

This article briefly reviews our current understanding of the evolution of magnetic fields in neutron stars, which basically defines the evolutionary pathways between different observational classes of neutron stars. The emphasis here is on the evolution in binary systems and the newly emergent classes of millisecond pulsars.     

Magnetic Fields of Neutron Stars

Astronomy Letters - The birth function of neutron stars in magnetic field $$B$$ is estimated for two models of the evolution of radio pulsars corresponding to different directions of evolution of...     

Microscopic Magnetic Dipole Radiation in Neutron Stars

There is a 3P2 neutron superfluid region in NS (neutron star) interior. For a rotating NS the 3P2 superfluid region is like a system of rotating magnetic dipoles. It will give out electromagnetic radiation, which may provide a new heating mechanism of NSs. This mechanism plus some cooling agent may give a sound explanation to NS glitches.     

Probable Inner Magnetic Structures of Magnetic Stars. I

In this paper we consider two-dipole inner structures of magnetic fields of magnetic stars obtained by modelling. A series of our papers on modelling the structures including this paper shows that there is an extraordinary variety of structures and parameters of stellarmagnetic fields.Actually, there are no two stars with exactly the same properties. This indicates a large variety of magnetized parent protostellar clouds, from which magnetic stars are formed.     

Cyclotron Lines: From Magnetic Field Strength Estimators to Geometry Tracers in Neutron Stars

With forty years since the discovery of the first cyclotron line in Her X-1, there have been remarkable advancements in the field related to the study of the physics of accreting neutron stars – cyclotron lines have been a major torchbearer in this regard, from being the only direct estimator of the magnetic field strength, a tracer of accretion geometry and an indicator of the emission beam in these systems. The main flurry of activities have centred around studying the harmonic separations, luminosity dependence, pulse phase dependence and more recently, the shapes of the line and the trend for long-term evolution in the line energy. This article visits the important results related to cyclotron lines since its discovery and reviews their significance. An emphasis is laid on pulse phase resolved spectroscopy and the important clues a joint timing and spectral study in this context can provide, to build a complete picture for the physics of accretion and hence X-ray emission in accreting neutron stars.     

Revisiting Field Burial by Accretion onto Neutron Stars

The surface magnetic field strength of millisecond pulsars (MSPs) is found to be about 4 orders of magnitude lower than that of garden variety radio pulsars (with a spin of \({\sim }\)0.5–5 s and \(B{\sim }10^{12}\hbox { G}\)). The exact mechanism of the apparent reduction of field strength in MSPs is still a subject of debate. One of the proposed mechanisms is burial of the surface magnetic field under matter accreted from a companion. In this article we review the recent work on magnetic confinement of accreted matter on neutron stars poles. We present the solutions of the magneto-static equations with a more accurate equation of state of the magnetically confined plasma and discuss its implications for the field burial mechanism.     

Investigation of Weakly Magnetic CP Stars. I

The magnetic fields of a sample of chemically peculiar stars, in which they had not been detected earlier, are reinvestigated on the basis of our own measurements and literature data. Despite the considerably higher measurement accuracy, again no magnetic fields were detected in any of them. An upper limit on the field of HD 10221 of 40 G was obtained. Despite the weakness of the fields, the parameters characterizing an anomaly in chemical composition correspond to those for strong fields. The same parameters in stars with strong fields generally correspond in value, although they are lower than expected in the case of HD 47152.     

Neutron Stars with a Quark Core. I. Equations of State

An extensive set of realistic equations of state for superdense matter with a quark phase transition is derived on the basis of the three equations of state for neutron matter and the eight variants of strange quark-gluon plasmas in the MIT quark bag model. The characteristics of the phase transitions are described and the calculated equations of state with a density jump are studied in detail.     

中子星的相对论平均场描述

从相对论平均场理沦出发,考虑核子、超子和介子的相互作用,研究了中子星的结构和性质以及超子耦合常数对中子星性质的影响.发现当密度较高时,中子星的核心区主要由超子组成,即中子星转变成以超子为主要成分的奇异中子星,并且这种转变受到超子相互作用的影响.当超子耦合常数与核子耦合常数的比值为0.65时,中子星转变为奇异中子星所对应的密度最小,此时计算的中子星的最大质量为1.4 M⊙,与天文观测结果较好符合.     

Buried Magnetic Field in Accreting Neutron Star

The evolution of the neutron star magnetic field is correlated to the accretion physical process in the binary X-ray phase. It is assumed that the original strong magnetic field is buried by the accreted materials, which is on account of the ferromagnetic physical property of the accreted matter. The obtained theoretical conclusions of our model are that: (1) the magnetic field decays in the X-ray binary phase, and relates inversely to the accreted mass as M^-1, (2) The internal magnetic field strength still remains large although the surface field strength decays.     

Dipped Magnetic Field Configurations Associated with Filaments and Barbs

In this paper, three-dimensional linear force-free field configurations that can be associated with filaments are considered. It is assumed that the field configurations are suitable to represent filaments if they contain magnetic dips. With the photospheric flux distribution chosen to be an arcade with a dextral/sinistral axial component, it is found that dipped configurations exist only for large values of alpha (where, ×B=B). The dips always lie above the polarity inversion line in the centre of the channel between the flux regions. When the dips are viewed from above to a depth of 1 Mm they resemble closely the shape of filaments viewed in absorption on the solar disk. As the magnitude of alpha increases, the horizontal and vertical extent of the dips also increases, giving active-region filaments for low values of alpha and quiescient filaments for high values of alpha. Dextral filaments only form for negative values of alpha and sinistral filaments for positive values of alpha. The portion of the field line that is dipped is always of inverse polarity and the magnitude of the field in the dipped region increases with height, both of which are consistent with Leroy, Bommier, and Sahal-Bréchot (1983). Overlying the region of dips there are arcades of normal polarity which have the correct left-bearing/right-bearing orientation for dextral/sinistral filaments. When the hypothesis of barbs occurring in dipped field lines is used, barbs that branch out of the main axis and to the right/left for dextral/sinistral filaments can be formed around minority polarity elements on either side of the polarity inversion line. No barbs are found around normal polarity elements. The model reproduces many of the observed features of filament channels, filaments and their barbs.     

Quantum Approach to Neutron Stars Leading to Configurations With Local Anisotropy and Mass Above the Oppenheimer-Volkoff Limit

The theory of stars consisting of non-interacting neutrons at zero Kelvin isrevisited starting from a quantum formulation. The Dirac equation is solvedin a curved space-time with spherical symmetry and N single-particle quantumstates are filled with N neutrons in such a way that the mass of the star isa minimum constrained by Einstein's equations of general relativity. Thisrule leads to quantum ground states with local isotropy (i.e. isotropicpressure) for masses below the Oppenheimer-Volkoff limit, but quantum groundstates with local anisotropy above it. The calculations suggest that thereare stable neutron stars with mass well above the currently accepted limit.     

Cooling of Accretion-Heated Neutron Stars

We present a brief, observational review about the study of the cooling behaviour of accretion-heated neutron stars and the inferences about the neutron-star crust and core that have been obtained from these studies. Accretion of matter during outbursts can heat the crust out of thermal equilibrium with the core and after the accretion episodes are over, the crust will cool down until crust-core equilibrium is restored. We discuss the observed properties of the crust cooling sources and what has been learned about the physics of neutron-star crusts. We also briefly discuss those systems that have been observed long after their outbursts were over, i.e, during times when the crust and core are expected to be in thermal equilibrium. The surface temperature is then a direct probe for the core temperature. By comparing the expected temperatures based on estimates of the accretion history of the targets with the observed ones, the physics of neutron-star cores can be investigated. Finally, we discuss similar studies performed for strongly magnetized neutron stars in which the magnetic field might play an important role in the heating and cooling of the neutron stars.     

Low-Mass Neutron Stars with Rotation

Astronomy Letters - The properties of low-mass neutron stars with rigid rotation are considered. The possible evolution paths of such stars in a close binary system with mass transfer are...     

Thermal Evolution of Neutron Stars

We present results from simulations of protoneutron star thermal evolution using neutrino opacities that are consistently calculated with the equation of state. When hyperons are allowed to appear in the system, we obtain metastable configurations that after the deleptonization stage become unstable. Concerning the evolution of old neutron stars, we present the results of our investigation on the effect of the Joule heating due to magnetic field dissipation. We conclude that this mechanism can be efficient in maintaining the surface temperature of the star above 3 × 10⁴ - 10⁵ K during a very long time (≥ 100 Myr), comparable with the decay time of the magnetic field. This revised version was published online in July 2006 with corrections to the Cover Date.