KMS of Xinjiang Astronomical Observatory, CAS
| 脉冲星的自行和间歇脉冲星自转减慢的研究 | |
| Alternative Title | Proper motions of pulsars and thespin-down of intermittent pulsars |
李琳
| |
| Subtype | 博士 |
| Thesis Advisor | 王娜 |
| 2016 | |
| Degree Grantor | 中国科学院大学 |
| Place of Conferral | 北京 |
| Degree Discipline | 天体物理 |
| Keyword | 自行 数据分析 间歇脉冲星 自转减慢 星风 |
| Abstract | 本文的工作主要分为两部分：第一部分是测定15颗脉冲星的自行：频率论和贝叶斯两种方法的比较；第二部分是星风模型对间歇脉冲星自转减慢行为的解释。 自行是重要的天体测量参数，自行以及由它得到的速度有助于了解脉冲星和与它成协的超新星爆发的状况，还有助于了解脉冲星的起源、诞生率、银河系前身星的分布、 运动学年龄、 脉冲星与星际介质之间的相互作用、 前身双星的性质及中子星的形成与演化等多个方面：在第一部分的工作里，我们测定了15颗年轻脉冲星的自行，观测数据来自新疆天文台南山25米射电望远镜的到达时间观测. 数据处理和分析采用了两种方法：频率论方法(Coles, Hobbs，Champion et al. 2011)和贝叶斯方法(Lentati, Alexander，Hobson et al. 2014)。我们比较了由两种方法获得的自行：结果非常一致，不仅测定的参数是一致的，参数的误差也相当一致。观测显示，年轻脉冲星通常表现出有大量的到达时间噪声（频谱为陡谱），这里我们展示了两种方法可以应用于年轻脉冲星，此前，它们都只应用于毫秒脉冲星，而我们知道毫秒脉冲星因其自转的稳定性，较少受到到达时间噪声的影响. 15 颗脉冲星中有4 颗脉冲星的自行是首次给出，5颗脉冲星的自行有改进。同时，我们也测定了这15颗脉冲星的位置，其中多数脉冲星的位置已有十年（有些已经超过二十年）没有更新过，并且由这些到达时间数据测得的脉冲星的位置也与基于甚长基线干涉测量推得的位置符合的很好。 第二部分的工作与间歇脉冲星有关. 观测上看，间歇脉冲星是“兼职的”射电脉冲星，因为它们的射电辐射呈现出两种明显不同的状态：on态（射电噪的状态）和off态（射电宁静的状态）。而且on和off两态交替出现，呈准周期性。最令人惊奇的是，比起off态，它们在on态时自转减慢的更快，这为粒子星风可能在脉冲星的自转减慢中发挥重要作用提供了证据. 我们在模拟间歇脉冲星的转动能损率时，考虑了粒子加速效应，并将脉冲星星风模型应用于三颗间歇脉冲星（PSR B1931+24，PSR J1841−0500 和PSR J1832+0029）。由此我们获得了它们在不同加速模型下的磁场和磁倾角，也从理论上给出了对应的制动指数。在星风模型中，粒子星风的密度可以总是Goldreich-Julian电荷密度，这可以确保间歇脉冲星on态的稳定性. 粒子星风的活跃占空比可以从到达时间的观测获得，这与on态的活跃占空比是一致的。未来，间歇脉冲星磁倾角和制动指数的观测将有助于检验粒子加速的不同模型. 目前，饱和场下空间有限电荷流诱导的逆康普顿散射的模型已经可以排除。 |
| Other Abstract | Two parts are included in this thesis, the first is proper motions of 15 pulsars：a comparison between frequentist and Bayesian algorithms, the second is on the pulsar wind model for the spin-down of intermittent pulsars. Proper motion is one of important astrometric parameters. The proper motions and the velocities derived from them can be used to trace a pulsar back to its birthplace and hence to check its association with a supernova remnant, clearly give information about the origin of pulsars, birthrate of pulsars and about the galactic distribution of the progenitor population. They can also be used to derive an independent measure of a pulsar’s kinematic age, the interaction between pulsars and interstellar medium, the progenitor binary properties and the formation of neutron stars to the details of their ageing. In the first part, we present proper motions for 15 pulsars which are observed regularly by the Nanshan 25-m radio telescope. Two methods, the frequentist method (Coles, Hobbs, Champion et al. 2011) and the Bayesian method (Lentati, Alexander, Hobson et al. 2014), were used and the results were compared. The results from both methods are remarkably consistent - both in terms of the parameter values and in terms of their uncertainties. We demonstrate that the two methods can be applied to young pulsar data sets that exhibit large amounts of timing noise with steep spectral exponents. Before that, the two methods are used only for millisecond pulsars which are highly stable in rotation with little noise. Proper motions for four pulsars are obtained for the first time, and improved values are attained for five pulsars. We note that the previously published positions for most of the 15 pulsars in our sample have not been updated for 10 to 20 years. The measured positions also agree with very-long-baseline interferometric positions. Intermittent pulsars are part-time radio pulsars. There are two different states: on state (radio-loud) and off state (radio-quiet), between which they switch quickly. The quasi-periodicity is exhibited in their switches. Most astonishingly, they have higher slow down rate in the on state than in the off state. This gives the evidence that particle wind may play an important role in pulsar spin-down. The effect of particle acceleration is included in modeling the rotational energy loss rate of the neutron star. Applying the pulsar wind model to the three intermittent pulsars (PSR B1931+24，PSR J1841−0500，and PSR J1832+0029), their magnetic field and inclination angles are calculated simultaneously. The theoretical braking indices of intermittent pulsars are also given. In the pulsar wind model, the density of the particle wind can always be the Goldreich-Julian density. This may ensure that different on states of intermittent pulsars are stable. The duty cycle of particle wind can be determined from timing observations. It is consistent with the duty cycle of the on state. Inclination angle and braking index observations of intermittent pulsars may help to test different models of particle acceleration. At present, the inverse Compton scattering induced space charge limited flow with field saturation model can be ruled out. |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.xao.ac.cn/handle/45760611-7/1718 |
| Collection | 研究生学位论文 射电天文研究室 |
| Affiliation | 中国科学院新疆天文台 |
| Recommended Citation GB/T 7714 | 李琳. 脉冲星的自行和间歇脉冲星自转减慢的研究[D]. 北京. 中国科学院大学,2016. |
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| File Name/Size | DocType | Version | Access | License | ||
| 李琳-学位论文.pdf（2830KB） | 学位论文 | 暂不开放 | CC BY-NC-SA | Application Full Text | ||
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