WoU-MMA: Studying Neutron Stars through the Lens of Nuclear Reactions

中子星是经历超新星爆炸的大质量恒星的残余物，其质量与我们的太阳相似，但半径只有12公里左右。它们的质量和半径之间的关系是由组成这些恒星的核物质的性质决定的，这些性质仍在研究中。这些超高密度的物体为研究这种致密核材料的性质提供了一个独特的窗口。LIGO-VIRGO合作对两颗中子星合并产生的引力波进行了开创性的测量，以及随后的多信使观测，极大地扩展了我们对核物质的理解。研究小组将对核反应进行实验室测量，以解决关于中子星组成及其过程的两个重要问题。这项工作将补充LIGO-VIRGO引力波测量提供的限制，以及美国宇航局资助的中子星内部成分探测器（NICER）的新结果。该项目位于核科学和天体物理学的交叉点，解决了国家科学基金会大构想“宇宙之窗”的科学案例。这项工作的跨学科性质将有助于吸引各种各样的研究生和本科生。这些学生将接受的培训将为他们广泛的职业生涯做好准备。特别是，这些年轻科学家的招聘和教育对于解决该国核化学家持续短缺的问题至关重要。该团队将在新的稀有同位素光束设施中利用重离子碰撞稀有同位素光束来提供对称能量密度和动量依赖的实验室约束。这是核状态方程（EoS）的组成部分，它解释了中子和质子数量不等的系统。目前，对称能是EoS中不确定性最大的组成部分。将这些结果与现有的反应、结构和天体物理观测结果相结合，将大大加强对EoS接近正常核密度的限制，这是对中子星科学最重要的密度。这项工作还侧重于理解i型x射线暴（XRB）的关键反应，现在可以通过直接方法获得。需要测量XRBs中特定的、重要的等待点的捕获横截面，以了解其光曲线的双峰性质。该团队将测量30S（α,p）反应的截面，这是重要的等待点之一。这个横截面没有被直接测量过。这种测量也将限制模拟XRBs重要反应所需的光学势。XRBs的测量也约束了中子星的质量-半径关系。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Neutron stars are the remnants of massive stars that have undergone a supernova explosion, resulting in an object that is similar in mass to our own sun, but has a radius of only about 12 km. The relationship between their mass and radii is determined by the properties of the nuclear matter that composes these stars, which is still under investigation. These super-dense objects provide a unique window to study the nature of this dense, nuclear material. The ground-breaking measurement of the gravitational waves originating from the merger of two neutrons stars by the LIGO-VIRGO collaboration, and the subsequent multi-messenger observations, significantly expanded our understanding of nuclear matter. The research team will perform laboratory measurements of nuclear reactions to address two important questions on the composition of neutron stars and their processes. This work will complement the constraints provided by the gravitational wave measurements from LIGO-VIRGO, as well as the new results from the NASA funded Neutron star Interior Composition Explorer (NICER). The project sits at the intersection of nuclear science and astrophysics, addressing the science case of the NSF Big Idea “Windows on the Universe.” The interdisciplinary nature of the work will help attract a diverse set of graduate and undergraduate students. The training these students will receive will prepare them for a wide range of careers. In particular, the recruitment and education of these young scientists is critical to address an ongoing shortage of nuclear chemists in the country.The team will utilize heavy-ion collisions with rare-isotope beams at the new Facility for Rare Isotope beams to provide laboratory constraints on the density and momentum dependence of the Symmetry Energy. This is the component of the nuclear equation of state (EoS) that accounts for systems of unequal amounts of neutrons and protons. At present, the Symmetry Energy is the component of the EoS with the largest uncertainty. Combining these results with the existing results from reactions, structure, and astrophysical observations will significantly tighten the constraints on the EoS near twice normal nuclear density, the density regime most important to the science of neutron stars. This work also focuses on a key reaction to understand type-I X-ray Bursts (XRB), now accessible by direct methods. The measurement of the capture cross sections on particular, important waiting points in XRBs are needed to understand the double-peaked nature of their light curves. The team will measure the cross section for the 30S(α,p) reaction, which is one of the important waiting points. This cross section has not been measured directly. This measurement will also constrain the optical potentials needed to model the reactions important for XRBs. The measurements of XRBs also constrain the mass-radius relationship of neutron stars.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.