[论文解读] The X-ray behaviour of Fermi/LAT pulsars

M. Marelli|arXiv (Cornell University)|May 8, 2012

Geophysics and Gravity Measurements被引用 15

一句话总结

本论文通过多波段分析研究费米/LAT脉冲星的X射线特性，结合X射线与伽马射线数据，探讨光度关系与光谱行为。研究揭示了射电安静与射电明亮脉冲星之间在X射线与伽马射线光度上的显著差异，其中射电安静源表现出更高的X射线与伽马射线流量比，并且自旋损失功率与X射线光度之间具有更紧密的相关性。

ABSTRACT

More than 40 years after the discovery of Isolated Neutron Stars, the comprehension of their physics is still rather poor. This thesis is based on a program of multiwavelength observations of pulsars which yielded new and important pieces of information about the overall proprieties of this class of sources. The thesis is organized as follows: - In chapter 1 we give a very brief overview of the current status of the understanding of Isolated Neutron Stars. We also talk about the Fermi revolution that occurred in the last three years, focusing on the Fermi contribution to the knowledge of neutron stars. Then, we describe the results led by the synergy between X-ray and gamma-ray bands. - In chapter 2 we report two of our published papers containing the surprising results we obtained for two different radio-quiet pulsars. Such neutron stars, J0007+7303 and J0357+3205, can be considered "extreme" in the Fermi pulsars' zoo due to their energetics and ages. Both the X-ray observations and analyses are very different so that they can be considered as the standing-up examples of all the following analyses. - In chapter 3 we describe the analysis we done in the X-ray band and briefly report the obtained spectra of each pulsar and its nebula, if present. Then, we study the X-ray and gamma-ray pulsars' luminosities as a function of their rotational energies and ages in order to find any relationship between these values and any difference between the two populations of radio-quiet and radio-loud pulsars. - In chapter 4 we report the "identity card" of all Fermi pulsars, the detailed description of the analyses done and results obtained for each pulsar. Finally, in appendix we report our accepted proposals of the most significative X-ray observations used in this thesis plus the article on the X-ray behaviour of Fermi/LAT pulsars we published on the Astrophyisical Journal.

研究动机与目标

• 理解费米/LAT脉冲星的多波段行为，特别是X射线与伽马射线波段的行为。
• 通过X射线与伽马射线光度相关性，研究射电安静与射电明亮脉冲星之间的物理差异。
• 考察自旋损失功率与年龄在塑造孤立中子星X射线与伽马射线辐射中的作用。
• 识别并表征极端脉冲星（如J0007+7303与J0357+3205）作为极端能量与年龄的案例研究。
• 评估脉冲星探测中的选择效应及其对光度函数解释的影响。

提出的方法

• 对两个极端射电安静脉冲星J0007+7303（CTA1）与J0357+3205（MORLA）进行了详细的X射线测时与相位分辨光谱分析。
• 利用钱德拉、XMM-牛顿与雨燕的观测数据，对单个脉冲星进行X射线数据还原与光谱分析。
• 构建$̕$-LX与$̕$-Lγ图以研究自旋损失功率（$̕$）与X射线/伽马射线光度之间的相关性。
• 计算33个高置信度脉冲星的$̶$-到X射线流量比（Fγ/FX），以比较不同群体的辐射机制。
• 应用几何校正因子，并使用I型/II型X射线光谱分类以评估光谱复杂性。
• 对对数-对数光度关系进行统计拟合，并在图表中包含上下限以处理未检测到的源。

实验结果

研究问题

• RQ1 费米/LAT脉冲星的X射线与伽马射线光度如何与它们的自旋损失功率（$̕$）相关？
• RQ2 射电安静与射电明亮脉冲星在X射线与伽马射线发射特性上存在哪些差异？
• RQ3 Fγ/FX流量比在不同脉冲星群体中如何变化？它揭示了何种辐射机制？
• RQ4 选择效应在塑造观测到的光度函数与相关性中起到什么作用？
• RQ5 像J0007+7303与J0357+3205这样的极端脉冲星在光谱与测时行为上与一般脉冲星群体有何不同？

主要发现

• 射电安静脉冲星在对数-对数空间中表现出比射电明亮脉冲星更紧密的自旋损失功率（$̕$）与X射线光度（LX）相关性，最佳拟合斜率约为0.7。
• 射电安静脉冲星的中位Fγ/FX流量比约为1.3，显著高于射电明亮脉冲星（中位约0.2），表明其相对于伽马射线具有更强的X射线发射。
• J1836+5925（费米J1836-1256）表现出最高的伽马射线流量比（Fγ/FX = 2.3 ± 0.1），表明其相对于X射线具有高效的伽马射线产生能力。
• 对于具有高置信度距离估计的脉冲星，X射线光度（LX）与$̕$在射电安静与射电明亮群体中均表现出强烈相关性，但归一化值不同。
• X射线与伽马射线流量比（Fγ/FX）与特征年龄呈负相关，尤其在射电安静脉冲星中更为明显，表明其光谱随时间演化。
• 对若干脉冲星（如J1811-1926、J1813-1749）的X射线流量上限与未检测结果一致，支持使用流量比分析来区分不同群体。