KMS of Xinjiang Astronomical Observatory, CAS
| 部分特殊脉冲星的演化研究 | |
| Alternative Title | Evolution of some Special Pulsars |
黄海涛
| |
| Subtype | 硕士 |
| Thesis Advisor | 周霞 |
| 2022-05-25 | |
| Degree Grantor | 中国科学院大学 |
| Place of Conferral | 北京 |
| Degree Name | 理学硕士 |
| Degree Discipline | 天体物理 |
| Keyword | 脉冲星，中子星，自转演化，热演化，磁场演化 |
| Abstract | 脉冲星是一类快速旋转、高度磁化的致密天体，其理论对应体为中子星。中子星内部物质处于极度致密的环境，由于其同时集强相互作用、弱相互作用、电磁作用和引力作用四种基本相互作用于一身，是天体物理、粒子物理和核物理天然的理想实验室，相关研究一直是天文领域的前沿及热门。 脉冲星的观测覆盖了从射电到γ射线的全电磁波波段，GW170817事件引力波信号的探测则开启了脉冲星观测的多信使时代。这些丰富的脉冲星观测给出了许多有趣的现象，如磁星的软γ射线暴、RRAT (Rotating Radio Transients)射电辐射的重复发射、LMXB (Low Mass X-ray Binary)中的X射线暴和致密双星系统的引力波辐射等。同时脉冲星具有大范围的自转周期分布（1.396 ms-23.5 s），且在P-dP/dt图上呈现聚类分布，表现为多个族群。同一类型的天体为何会表现出如此多的不同特征？有着如此大范围的周期分布？以及是如何演化出如此多的族群？ 以往的工作指出PSR B0950+08是一颗年老高温的脉冲星，而近期的研究显示其动力学年龄比特征年龄要小一个量级；PSR J0250+5854 和PSR J2251–3711是两颗新近发现的长周期脉冲星，周期分别为23.5 s和12.1 s，并且它们在P-dP/dt图上处于典型的XDINS (X-ray Dim Isolated Neutron Star)的位置，却只有射电辐射而没有在X 射线波段被探测到。本工作以这三颗特殊脉冲星为例，重点考虑转动演化与热演化的耦合效应，结合射电与X射线热辐射的观测数据，研究不同脉冲星演化模型，期望得到不同脉冲星族群之间的联系，限制部分脉冲星演化的关键参数，揭示脉冲星可能的起源。 我们利用新疆天文台南山26米射电望远镜对PSR B0950+08近14年的测时观测数据，给出其计时观测结果，结果显示制动指数有着大范围变化（-367392~168883），并表现出准周期振荡的行为。通过对比，我们发现短周期振荡调制的长时标磁场衰减模型能解释该源自转频率导数和制动指数的振荡及年龄等问题。结合PSR B0950+08的年龄和表面温度，我们认为：对于偏小的动力学年龄而言，无需额外的加热机制即可解释其表面温度，并可限制其年龄为：(2.87-5.58) Myr；对于其特征年龄而言，化学加热和涡丝爬行加热能合理解释其年老高温问题。涡丝爬行加热机制使脉冲星能在老年阶段保持一个较高温度；在化学加热机制下，表面温度限制PSR B0950+08的年龄为：(17.10-17.19) Myr，并给出其初始自转周期P0< 17ms。 对于长周期脉冲星PSR J0250+5854和PSR J2251--3711，我们对比了四种不同的制动机制：磁场衰减模型、磁倾角演化模型、回落盘吸积模型和r模不稳定性，在P-dP/dt图上得到了各自对应的演化路径，成功解释了其自转周期及周期导数。结合其热辐射光度上限，我们发现：(1)在磁场衰减模型下PSR J0250+5854和PSR J2251--3711可能由磁星演化而来，磁场衰减的磁能释放提供了热辐射光度的能量来源。(2)磁倾角演化模型下PSR J0250+5854可能由磁星或普通射电脉冲星演化而来，而PSR J2251--3711很有可能一直是一颗射电脉冲星。(3)回落盘模型能够解释热辐射的光度上限，却无法解决在吸积相仍有射电辐射的问题。(4)r模不稳定性对脉冲星演化产生作用的时间段为~102 yr，对于PSR J0250+5854和PSR J2251--3711长时标的热演化，r模不稳定性的影响在晚期可以忽略不计。 |
| Other Abstract | Pulsar are a class of highly magnetized and rapidly rotating compact objects, whose counterpart is neutron star in theory. There is a highly dense environment inside neutron stars, where with the four fundamental interactions, including strong interaction, weak interaction, electromagnetic interaction and gravitational interaction, which make neutron stars become the ideal laboratory of astrophysics, particle physics and nuclear physics, so neutron star always is the forefront and hotpot of astronomical research. The observations of pulsars cover the whole electromagnetic spectrum from radio to γ-rays, and the detection of gravitational-wave signals from the GW170817 event ushered in the multi-messenger era of pulsar observations. These abundant pulsar observations reveal many interesting phenomena, such as soft gamma-ray bursts from magnetars, repeated radio emission of RRAT (Rotating Radio Transients), X-ray bursts in LMXB (Low Mass X-ray Binary) and gravitational wave radiation from binary systems of compact stars. At the same time, there is an extensive range of rotation period distribution (1.396 ms-23.5 s) of pulsars and a cluster distribution on the P-dP/dt diagram, which shows the multiple populations. Why do the neutron stars exhibit so many different features? And with such a wide range of periodic distributions? Furthermore, how did it evolve to so many populations? PSR B0950+08 is suggested to be an old but still warm pulsar in the previous work, but recent research shows that the characteristic age of PSR B0950+08 is an order of magnitude older than its kinematic age; PSRs J0250+5854 and J2251-3711 are two long spin period pulsars which be detected recently, with spin period as 23.5 s and 12.1 s, respectively. Both of PSRs J0250+5854 and J2251-3711 are located in typical XDINS (X-ray Dim Isolated Neutron Star) position on the P-dP/dt diagram, but with only detection in radio and without detection in X-ray.Taking the specific pulsars PSRs B0950+08, J0250+5854 and J2251–3711 as examples, this work focus on the coupling of rotational evolution and thermal evolution, and combine with the observation data of radio and X-ray, to study different pulsar evolution models, expect to obtain the relationship between different pulsar populations and to reveal the origin of pulsars. We present the timing solutions of PSR B0950+08 by using 14 years of observations from the Nanshan 26-m Radio Telescope of Xinjiang Astronomical Observatory, which suggest the braking index varies with a large range (-367392~168883) and show quasi-period oscillations. A model of magnetic field with long-term decay modulated by short-term oscillation be proposed to explain the issue of timing data of PSR B0950+08, including its age and the quasi-period oscillations of its spin frequency derivative and braking indices. Combining with the age and the surface temperature of PSR B0950+08, we present that: The standard cooling model could explain the surface temperature of PSR B0950+08 with its kinematic age, and constrain the age of PSR B0950+08 as (2.87-5.58) Myr; The roto-chemical heating and vortex creep heating can account for the surface temperature of PSR B0950+08 with its characteristic age. The vortex creep heating with the magnetic field decay could maintain a relatively high temperature at the later stages. The roto-chemical heating with magnetic field decay constrain the age of PSR B0950+08 as (17.10-17.19) Myr, and constrain its initial spin period as P0 < 17ms. For the long spin-period pulsar PSR J0250+5854 and PSR J2251–3711, we compare four different braking mechanisms: magnetic field decay model, obliquity angle evolution model, fall-back disk accretion model and r-mode instability, and obtain the corresponding evolution paths on the P-dP/dt diagram, which explains the spin period and its derivatives successfully. Combining with the upper limit of the thermal emission luminosity, we present that: (1) The evolution of pulsars under the magnetic field decay model indicates a possible connection between PSRs J0250+5854, J2251-3711 and high dipole-magnetic field magnetars and the magnetic energy released through magnetic field decay provides the energy of thermal radiation. (2) PSR J0250+5854 may come from magnetar or normal radio pulsar, and PSR J2251-3711 always is a normal radio pulsar with obliquity angle decay model. (3) The fall-back disk model can explain the upper limit of the thermal radiation luminosity. However, it is hard to explain that the pulsar is simultaneously in the accretion and radio phases. (4) R-mode instability effect the evolution of puulsars with the timescale as about ~102 yr, namely that the influence of r-mode instability to the thermal evolution of PSRs J0250+5854 and J2251-3711 can be ignored at the later stages. |
| Pages | 80 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.xao.ac.cn/handle/45760611-7/5166 |
| Collection | 研究生学位论文 射电天文研究室_脉冲星研究团组 |
| Affiliation | 中国科学院新疆天文台 |
| First Author Affilication | Xinjiang Astronomical Observatory, Chinese Academy of Sciences |
| Recommended Citation GB/T 7714 | 黄海涛. 部分特殊脉冲星的演化研究[D]. 北京. 中国科学院大学,2022. |
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| 部分特殊脉冲星的演化研究_黄海涛.pdf（5683KB） | 学位论文 | 暂不开放 | CC BY-NC-SA | Application Full Text | ||
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