Probing Extreme Physics Through Analysis of Neutron Star Surface Emission

中子星呈现了宇宙中一些最极端的物理条件--这些条件不能通过地球上的实验室实验来研究。在这里，Bhattacharyya博士和他的合作者将专注于三个只有通过研究中子星才能解决的具体问题：(1)了解中子星核心中的超高密度冷物质，其中可能包含奇异物质(例如介子凝聚、去禁闭夸克等)。这是一个35年多来一直没有解决的基础物理问题，只有通过精确测量中子星的质量、半径和自旋周期才能解决。(2)对广义相对论的预言进行强场检验。(3)了解I型X射线爆发期间热核火焰如何在中子星表面扩散，这也将为探索极端条件下磁化大气的行为提供独特的机会。这些研究将对包括核物理、磁流体动力学和广义相对论在内的各个领域产生重大影响。在头两年，该小组将进行：对来自Rossi X射线定时探测器(RXTE)卫星的I型爆发数据进行详尽的分析，并将观测到的快速计时特征和宽带光谱与该小组已经开发的严格模型同时进行拟合(这将限制中子星的性质)；仔细分析Chandra和X射线多镜-牛顿卫星的数据，以确定燃料的化学成分和I型爆发的其他方面，并从中子星表面搜索光谱线(两者都将有助于约束恒星参数)；对表面光谱线的形状进行了详细的理论研究，以规定一种现实的方法来探测广义相对论预测的帧拖曳，并估计未来X射线卫星对这种探测的能力；并在RXTE数据档案中找到每一类I型爆发的各种爆发特性的显著时间演变(这将有助于理解火焰传播)。在第三年，该小组将专注于：对吸积毫秒脉冲星的持续脉动光曲线进行建模(这将涉及散射日冕中的一般相对论射线跟踪，并将约束中子星参数)；以及包括磁场影响的火焰传播模拟，以便对RXTE数据进行建模。这些项目可能会在极端条件下物质的行为方面取得突破。预计这项研究将对物理学的几个领域产生影响。它具有在不同学科和机构之间建立合作的强大潜力。该小组将通过在期刊上发表文章和在科学会议上发表演讲来传播科学成果。该团队还将在流行期刊上讨论他们的发现，并在马里兰大学天文台和其他论坛上发表公开演讲。

Neutron stars present some of the most extreme physical conditions in the universe - conditions which cannot be studied through laboratory experiments here on Earth. Here Dr. Bhattacharyya and collaborators will focus on three specific problems which can only be addressed by studying neutron stars: (1) understanding the super-dense cold matter in neutron star cores, which may contain exotic matter (e.g., meson condensates, deconfined quarks, etc.). This has been an unsolved problem of fundamental physics for more than 35 years, and can be resolved only by accurate measurements of the mass, radius and spin period of a neutron star. (2) Performing strong-field tests of the predictions of general relativity. (3) Understanding how thermonuclear flames spread on neutron star surfaces during type I X-ray bursts, which will also provide unique opportunities to probe the behavior of magnetized atmospheres under extreme conditions. These studies will have significant impact on various fields, including nuclear physics, magnetohydrodynamics, and general relativity. In the first two years, the team will carry out: an exhaustive analysis of type I burst data from the Rossi X-ray Timing Explorer (RXTE) satellite, and the simultaneous fitting of the observed fast timing features and broad-band spectra with the rigorous models already developed by the team (this will constrain properties of neutron stars); a careful analysis of data from Chandra and X-ray Multi-Mirror-Newton satellites to determine the chemical composition of the fuel and other aspects of the type I bursts, and to search for spectral lines from neutron star surfaces (both will be useful for constraining stellar parameters); detailed theoretical study of the shapes of surface spectral lines for prescribing a realistic way to detect the frame-dragging predicted by general relativity, and estimation of the capabilities of future X-ray satellites for this detection; and finding significant time evolution of various burst properties for each type I burst in the RXTE data archive (this will aid in the understanding of flame spreading). In the third year, the team will focus on: the modeling of persistent pulsation light curves from accreting millisecond pulsars (this will involve general relativistic ray tracing in a scattering corona, and will constrain neutron star parameters); and simulation of flame spreading including the effects of magnetic fields, in order to model the RXTE data. These projects may yield a breakthrough in the behavior of matter in extreme conditions.It is expected that this research will have an impact on several fields of physics. It has strong potential to establish collaborations among different disciplines and institutions. The team will disseminate the scientific results through publications in journals and presentations at scientific meetings. The team will also discuss their findings in popular journals, and give public talks at the University of Maryland Observatory and in other forums.