Neutron Star Astrophysics

中子星是在超新星中诞生的非凡物体，当一颗大质量的星星在其生命的尽头坍缩时。大质量星星的核心在自身引力的作用下收缩，直到半径只有10公里，但仍然包含与太阳一样大的质量。中子星星内部的中子和质子比原子核中的中子和质子更接近，因此中子星是研究强核力的重要实验室。中子星也很重要，因为它们附近的极端条件：强引力，强磁场和快速旋转。** 这里提出的研究是对中子星内部和周围物理过程的调查。目标是找出中子星内部的致密物质是什么样的，理解为什么许多中子星都是磁性活跃的（就像我们的太阳的极端版本），并将中子星作为实验室来研究极端条件。我们通过建立我们认为在中子星内部发生的过程的理论模型来做到这一点，然后将其与天文观测进行比较，通常使用轨道X射线望远镜。** 特别感兴趣的是双星系统中的中子星。如果中子星星的轨道离它的伴星星星足够近，伴星表面升起的巨大潮汐会导致气体流向中子星星。氢和氦在中子星星的表面积累了几个小时，然后经历了热核失控，迅速燃烧并引起了持续几秒钟的X射线的明亮闪光。在这几秒钟内，我们可以直接看到中子星星并对其进行研究。该提案中的一个项目是了解星星在经历其中一次闪光时从其表面驱动的等离子体风。通过X射线观测，我们可以尝试测量中子星星的半径，并由此计算出其核心的密度。** 一些中子星有很强的磁场，并显示出类似于我们太阳的耀斑和喷发。这是相当令人惊讶的，因为中子星星应该有一个相对平静的表面，不像太阳，太阳的外层是对流的，所以等离子体不断地冒泡到表面，干扰磁场。不知何故，中子星也有磁性。我们希望通过研究中子星星在加热事件后冷却的速度来找出原因。

Neutron stars are remarkable objects born in supernovae when a massive star collapses at the end of its life. The core of the massive star shrinks under its own gravity until it is only 10km in radius, but still contains as much mass as the Sun. The neutrons and protons inside the neutron star are closer together than in the nucleus of an atom, and so neutron stars are important laboratories for studying the strong nuclear force. Neutron stars are also important because of the extreme conditions in their vicinity: strong gravity, strong magnetic fields, and rapid spin. ******The research proposed here is an investigation of physical processes in and around neutron stars. The goal is to find out what the dense matter inside neutron stars is like, understand why many neutron stars are magnetically active (like an extreme version of our Sun), and to use neutron stars as laboratories to investigate extreme conditions. We do this by making theoretical models of processes that we think are happening inside neutron stars and then comparing to astronomical observations, often with orbiting X-ray telescopes. ******Of particular interest are neutron stars in binary systems. If the neutron star orbits close enough to its companion star, the huge tides raised on the surface of the companion cause gas to flow onto the neutron star. The hydrogen and helium builds up on the surface of the neutron star for a few hours and then undergoes a thermonuclear runaway, rapidly burning up and causing a bright flash of X-rays lasting a few seconds. For those few seconds, we can see the neutron star directly and study it. One of the projects in this proposal is to understand the plasma wind that is driven from the surface of the star as it undergoes one of these flashes. By observing in X-rays, we can try to measure the radius of the neutron star and from there work out the density of its core. ******Some neutron stars have strong magnetic fields and show flares and eruptions similar to our Sun. This is quite surprising because a neutron star should have a relatively calm surface, unlike the Sun whose outer layers are convective so that plasma is continuously bubbling up to the surface and disturbing the magnetic field. Somehow neutron stars are also magnetically active. We hope to find out why by studying how quickly the neutron star cools down after a heating event.**