Evolution of Pulsars with Energy Release in the Superfluid Core of a Neutron Star

The effect of a neutron-proton vortex system on the rotation dynamics of neutron stars is examined. The dynamics of the motion of a two component superfluid system in the core of a neutron star yields an equation for the evolution of the pulsar's rotation period. The spin down of the star owing to energy release at the core boundary, which is associated with a contraction of the length of the neutron vortex as it moves radially and magnetic energy of the vortical cluster is released, is taken into account. Evolutionary curves are constructed for pulsars with different magnetic fields and stellar radii. For certain values of the coefficient of friction between the superfluid and normal components in the core of the neutron star, at the end of its evolution a radio pulsar may become an anomalous x-ray pulsar or a source of soft gamma radiation with a period on the order of 10 seconds.     

Comparing Black Hole and Neutron Star Variability

There are remarkable similarities between the rapid X-ray variability of low-magnetic field neutron stars in low mass X-ray binaries, and that of black holes. In particular at frequencies < 100 Hz, their power spectra can be strikingly similar. The highest frequency phenomena (kilohertz QPOs, black hole high-frequency QPOs and neutron star hectohertz QPOs) are the ones that show most differences, perhaps because they originate closest to the compact object. Most variability components vary in frequency in correlation with one another, and the correlations once again are very similar across neutron stars and black holes – some extend even to white dwarfs. Although this does not strictly require that all phenomena whose frequencies are involved are caused by the same physics in all three source types, this does indicate that basic properties of the accretion flow which are the same in all three source types play an important role in generating at least some of the frequencies.     

An Upper Bound on Neutron Star Masses

We derive an upper bound on neutron star masses by using model equations of state in the nuclear matter density region and the causality limited equation of state in the ultradense region. Supposing that the model equations of state describe neutron star matter at nuclear matter density correctly we find as bound 3.75 M_⊙. For large fiducial densities one gets a maximum mass which is above a previous estimate.     

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.     

超新星SN 1987A的热光度演化──内部中子星的贡献

本文介绍了超新星SN1987A爆发六年多来其热光度演化的研究情况．爆发后的前800天，观测的热光度曲线与由超新星爆发时合成的放射性元素的放射衰变加热模型符合得很好．但900天以后，观测的热光度曲线比考虑了所有放射性元素贡献后的理论曲线下降得还要缓慢．这可能表明有新的能源在起作用．我们认为这个新的能源可能是超新星爆发时产生的中子星的吸积．通过吸积超新星爆发时抛射气壳中小于逃逸速度的部分物质而增大SN1987A的热光度．这一模型能很好地解释900天以后的光度曲线的下降变级以及900至1200天之间光度曲线的凸起，这也为内部中子星的存在提供了间接的证据．     

磁中子星的一维吸积柱模型

本文给出了改进的一维吸积柱模型,探讨了在大吸积率下吸积柱的结构及物理性质,并理论推导吸积柱内下落物质的温度、密度及速度的变化．计算结果表明,它自上而下可以分为几个部分：冲击区（辐射压减速区）、理想气体压减速区、简并气体压减速区、外流区．作为例证,详细计算了吸积率Ｍ≈１０~１７ｇ／ｓ,极区磁场强度Ｂｍ≈１０~８Ｔ的中子星吸积柱．探讨了吸积柱内的热核反应,认为它可能与低质量Ｘ射线双星的低频ＱＰＯ（准周期振荡）现象有关．     

估算有中子星作伴星的黑洞质量

在本文中，我们讨论了由中子星和黑洞构成的密近双星系统的引力效应。首先，我们清楚地解释了引力辐射存在引起的轨道圆化，并估算了圆化的时间尺度。求解了围绕史瓦西黑洞作圆轨道运动的矢量进动方程，得到了一个精确解。由进动周期和中心黑洞的质量的关系，我们得到了估算中子星伴随的黑洞质量的方法。随后我们讨论了以中子星脉冲信号随自旋进动变化来寻找黑洞的方法。     

Explosion of a Minimum-Mass Neutron Star within Relativistic Hydrodynamics

Astronomy Letters - The relativistic hydrodynamics equations are adapted for the spherically symmetric case and the Lagrangian form. They are used to model the explosive disruption of a...     

Structure of the Magnetic Field of a Neutron Star

The magnetic field distribution in the superfluid, spherical, hadronic core of a rotating neutron star, which consists of vortex and vortex-free zones, is investigated. Due to the effect of entrainment of superconducting protons by rotating superfluid neutrons, a nonuniform magnetic field, the average value of which is constant, is formed in the vortex zone of the neutron star, directed parallel to the star's axis of rotation. It is shown that at the stellar surface, near the equatorial plane, there is a vortex-free zone of macroscopic size in which there is no magnetic field. The magnetic field near the boundaries of the vortex-free zone falls off exponentially with depth into the interior of this zone. This result essentially alters earlier concepts about the magnetic field distribution in the superfluid hadronic core of a neutron star. Outside the hadronic core the magnetic field has a dipole character with a magnetic moment on the order of 10³⁰ g×cm³.     

中子星中心致密天体的双星起源

探讨了认为中心致密天体(CCO)起源于双星的可能性.首先, CCO与正常遗迹脉冲星有着相似的平均自旋周期,但CCO的平均表面磁场强度(B～5.4×10~(10)Gs)低于正常遗迹脉冲星(B～7.7×10~(12)Gs)～2个量级.同时,几乎所有的正常遗迹脉冲星均分布在爱丁顿吸积加速线以上,而CCO全部分布在自旋加速线以下.因此怀疑CCO可能起源于双星吸积加速过程.其次,基于中子星再加速理论,分析了CCO可能的双星演化过程:双星系统中, CCO以M～1017g·s~(-1)的吸积率,经过～106yr的时间共吸积△M～10~(-2)M⊙的物质,其自旋周期将会从P～10 s降低至P～0.1 s,表面磁场强度将会从B～10~(12)Gs降低至B～1010Gs.考虑到～106yr的演化时标远大于CCO遗迹的年龄(～0.3–7 kyr),猜想CCO可能是双星系统中第1颗恒星超新星爆发的产物,而第2颗恒星超新星爆发后双星解体,留下CCO和第2颗恒星的超新星遗迹.该模型预言在CCO附近可能存在一颗年轻的正常脉冲星(P～0.02 s, B～1012Gs),并期望未来的射电望远镜和高能探测器能够进行搜寻.     

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.     

A Neutron Star Atmosphere in the Laboratory With Petawatt Lasers

We discuss the preliminary estimates to create Neutron Star atmospheric conditions in the laboratory and the possibility of generating photon bubbles. The minimal requirements for photon-bubble instability could potentially be met with a properly configured 10 ps petawatt laser experiment. The high energy (multi-MeV) electrons generated by an ultra-intense laser interacting with a foil are coupled to the electrons in the solid to heat the entire solid generating high thermal temperatures. Small amounts of matter could potentially be heated to ~1 keV temperatures with large radiation temperature. Additionally, 2-D PIC simulations show large B-fields on both the front and back of these targets with B fields consistent with experiments using the petawatt at Rutherford Appleton Laboratory (Tatarakis, M. et al.: 2002c, Nature 415, 280).     

Linear Wave Beams in the Crust of a Neutron Star

The propagation of axially symmetric wave beams near the equatorial plane of a neutron star is studied. These waves are excited by a spatially bounded perturbation in the form of a transverse magnetic field applied to the inner boundary of the crust of the star. For a small ratio of the perturbed to the unperturbed magnetic field, a linear theory can be employed to solve the evolution equation. This condition is satisfied in the crust plasma of a neutron star for typical radio luminosities of pulsars. The resulting simple, exact solution in the form of linear gaussian beams exists without additional conditions on the dissipation, dispersion, and narrowness of the beams, if the velocity c _n of these waves is constant. The latter requirement is well satisfied for the plasma in neutron star crusts. The width of the gaussian beam also depends weakly on position.     

Phenomenological Nucleon-nucleon Potentials and the Equation of State of Neutron Star Matter

We have calculated the equation of state of the neutron star matter and some of its properties for a wide range of nucleon-nucleon potentials using the lowest order constrained variational (LOCV) method. It turns out that for the UV ₁₄+TNI potential, the proton fraction exhibits a peak and falls off at high densities. The equation of state with the UV ₁₄+TNI potential is seen to be much harder than those with other potentials. The polytropic behaviour of the neutron star matter with various potentials are discussed. Compared with the other methods, the LOCV results show good agreement for densities below 0.7 fm _-3. Above this density, however, the differences with other methods are appreciable.     

What can we learn from Neutron Star X-Ray Binaries' JETS?

We review our current knowledge of the disk-jet coupling in neutron star X-ray binaries. We compare neutron star and black hole X-ray binaries, by means of radio and X-ray observations, in order to understand the role played in the production of the jet, by characteristics proper of the accreting compact object involved: the existence of a solid surface, the presence of an ergosphere/event horizon, the strength of the magnetic field, the spin of the compact object.     

Environments of Supernova Remnants Which Contain Different Types of Neutron Star

Understanding the formation and evolution of massive galaxies provides important keys to constrain the baryon assembly processes in the ΛCDM hierarchical scenario. We review the main results obtained so far with the K20 and other recent near-IR surveys on the redshift distribution, the evolution of the luminosity function and luminosity density, the nature of old and dusty EROs, the evolution of the galaxy stellar mass function and the nature of luminous starbursts at z∼2 which may be the progenitors of the present-day massive spheroidal galaxies.     

Constraining the Parameterized Neutron Star Equation of State with Astronomical Observations

We utilize the phenomenologically parameterized piecewise polytropic equations of state to study various neutron star properties.We investigate the compliance of these equations of state with several astronomical observations.We also demonstrate that the theoretical estimates of the fractional moment of inertia cannot explain all the pulsar glitches observed.We model the crust as a solid spheroidal shell to calculate the fractional moment of inertia of fast-spinning neutron stars.We also show th...     

中子星X射线双星中kHz QPO现象的理论解释

罗西X射线时变探测器(RXTE)在中子星小质量X射线双星中发现了千赫兹准周期振荡现象(kHzQPO)。kHzQPO的频率一般在几百到上千赫兹,其动力学时标与吸积盘最内部区域物质的运动时标一致,因此普遍认为kHz QPO产生于中子星表面附近区域,携带了来自中心中子星及周围强引力场信息,如质量、自转周期、角动量、半径、磁场等。kHz QpO现象的理解为研究强引力场和致密物质状态开启了一扇新的窗口。着重介绍基于kHz QPO的基本现象和相应的理论模型。     

On the Neutron Star/Black Hole Mass Gap and Black Hole Searches

Mass distribution of black holes in low-mass X-ray binaries previously suggested the existence of a ～2–5 M⊙mass gap between the most massive neutron stars and the least massive black holes, while some recent evidence appears to support that this mass gap is being populated. Whether there is a mass gap or not can potentially shed light on the physics of supernova explosions that form neutron stars and black holes, although significant mass accretion of neutron stars including binary mergers may l...     

OB星协和年轻星团的形成与早期演化

ＯＢ星协和年轻星团是恒星形成与早期演化的“化石”，同时也是研究初始重质量函数（ＩＭＦ）的最好场所；文中就ＯＢ星协和年轻星团的形成和早期演化方面的研究进展作了一评述，还论述了ＩＭＦ的测定和研究情况，并对相关的速逃ＯＢ星及蓝离散星问题作了简要介绍。