r模对LMXB吸积中子星演化的影响

发布时间：2017-12-31 08:23

本文关键词：r模对LMXB吸积中子星演化的影响　出处：《华中师范大学》2015年硕士论文　论文类型：学位论文

【摘要】：认识中子星的途径有很多种,本文重点考虑r模不稳定性。引力波辐射对模式的增长效应与粘滞耗散对模式的抑制效应之问的竞争决定了r模不稳定性能否产生。由于粘滞耗散时标是依赖于温度的,所以我们首先介绍中子星的热演化方程,中子星一方面通过中微子辐射和表面光子辐射而释放能量,另一方面,剪切粘滞耗散可以逐渐地把r模一部分振荡能量转化为热能,并且低质量X射线双星(LMXB)中的吸积中子星通过吸积也可以产生热能加热星体。随后,我们介绍了由星体的旋转频率和温度这两个物理量所决定的r模不稳定性窗口,给出了典型的r模不稳定性窗口以及LMXB中的吸积中子星在窗口中的演化,并根据观测到的数据,在考虑粘滞边界层耗散效应的基础上,对窗口进行了修正。我们通过求解线性和非线性流体力学方程得到的一阶和二阶r模演化方程,比较两者之间的差异。较差旋转能够使得星体内部的原初偶极磁场随着流体元的漂移而被扭曲,这个过程导致了一种新的r模阻尼机制——磁阻尼。第三章中,我们在给定星体内部原初磁场位型的基础上,结合二阶拉格朗日位移,推导出了新的环向磁场以及磁能的变化率,给出了二阶r模模型下的磁阻尼率。在此基础上考察了磁阻尼率对LMXB中的吸积中子星的r模演化、热演化以及旋转演化的影响。结果表明,环形磁场的存在会抑制r模不稳定性,使得星体自转减慢,同时还会降低r模的加热效果。随后,进一步考虑了由于磁场形变诱导星体产生引力波辐射,并在考虑粘滞边界层的耗散作用的基础上,再次考察了星体的演化。结果发现r模演化由之前长时问的振荡演化变成迅速增长并迅速衰减,这一变化时间持续大约几千年,这是由于考虑磁场形变导致的引力波辐射制动之后,吸积加速力矩不能和引力波制动力矩相抗衡,星体会很快的自转减慢,r模不会出现振荡。我们得到结论LMXB中的r模作用瞬间完成,r模引力波辐射受到抑制,但是LXMB中的吸积中子星的演化还是受到了较大的影响,温度演化、r模演化、旋转演化都会体现突出特征,特别是旋转极限频率能够与LMXB的观测结果相符合。
[Abstract]:There are many ways to know neutron stars. In this paper, the instability of r mode is mainly considered. The competition between the increasing effect of gravitational wave radiation on the mode and the restraining effect of viscous dissipation on the mode determines whether the instability of r mode can be produced. Because the viscous dissipation time scale is dependent on the. Temperature. So we first introduce the thermal evolution equation of neutron star. On the one hand, neutron star releases energy through neutrino radiation and surface photon radiation, on the other hand. Shear viscosity dissipation can gradually convert part of the oscillatory energy of the r mode into heat energy, and the accretion neutron stars in the low mass X-ray binary star LMXB can heat the stars by heat energy through accretion. We introduce the r-mode instability window, which is determined by the rotation frequency and temperature of the star, and give the typical r-mode instability window and the evolution of the accretive neutron star in LMXB. Based on the observed data and considering the dissipative effect of viscous boundary layer, the window is modified. The first and second order r-mode evolution equations are obtained by solving linear and nonlinear hydrodynamic equations. The difference between the two is compared. The differential rotation can distort the primary dipole magnetic field along with the drift of the fluid element, which leads to a new r mode damping mechanism, magnetic damping. In Chapter 3. On the basis of a given initial magnetic field potential type in the body, combined with the second order Lagrange displacement, we derive the rate of change of the new toroidal magnetic field and magnetic energy. The influence of magnetic damping rate on the r mode evolution, thermal evolution and rotation evolution of accretion neutron stars in LMXB is investigated. The existence of annular magnetic field will suppress the instability of the r-mode, slow down the rotation of the star, and decrease the heating effect of the r-mode. Subsequently, the gravitational wave radiation of the star induced by magnetic field deformation will be further considered. On the basis of considering the dissipation of the viscous boundary layer, the evolution of the stars is studied again. It is found that the evolution of the r-mode changes from the oscillatory evolution of the previous long time to the rapid growth and decay. This change lasted for about several thousand years, because the accretion acceleration torque could not compete with the gravitational wave braking moment after considering the gravitational wave radiation braking caused by the magnetic field deformation, and the star would quickly slow down its rotation. It is concluded that the r-mode gravitational wave radiation in LMXB is suppressed instantly, but the evolution of accretive neutron stars in LXMB is still greatly affected. Both the temperature evolution and the rotation evolution show outstanding characteristics, especially the rotation limit frequency can be consistent with the observed results of LMXB.
【学位授予单位】：华中师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P145.6

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