Binary Compact Objects and their Progenitors

恒星内部核反应产生的热量会产生压力，防止恒星在自身引力下坍塌。然而，所有恒星最终都会耗尽核燃料。当这种情况发生时，恒星在自身重量下坍塌，核心将形成非常致密、致密的残留物。根据恒星的质量，残留物要么是黑洞，要么是中子星，要么是白矮星。许多恒星是在双星系统中形成的，双星系统是两颗相互引力束缚的恒星。如果双星中的两颗恒星演化成致密天体，那么所产生的系统就被称为“致密天体双星”。在最近的天空观测中，紧密的旋涡合并的天体双星被观察到是明亮的瞬变，并被检测到是引力波的来源。加州理工学院(Caltech)的一个研究小组将研究这些紧凑双星系统的形成路径。他们的结果将限制影响这些系统演化的物理过程，这些过程决定了它们的引力波和电磁特征。该团队将致力于各种项目，旨在留住STEM领域中代表不足的少数族裔(URM)本科生。特别是，首席调查员(PI)将指导加州理工学院和邻近机构的URM本科生和研究生。PI还将参与加州理工大学新的未来点燃计划，旨在帮助有色人种学生为研究生院做准备，包括帮助加州理工大学的申请过程和研究机会。最后，国际和平协会将参加几项公共宣传活动。该团队将使用先进的计算技术来模拟双星致密天体的形成路径。他们将专注于了解轨道角动量(AM)是如何损失的，以使两个残余物螺旋并合并。具体地说，他们将：(1)对具有一定范围的白矮星质量、初始轨道周期和氢壳层质量的双星白矮星模型进行演化计算，以确定观测到的白矮星双星的后公共包络条件。(2)通过拉格朗日-2(L2)点将额外的AM损失落实到双星演化模型中，以解释物质在质量传输率足够高的情况下可以通过较高的拉格朗日点逃逸的事实。(3)运行包括氦(情况BB)转移的二元模型，包括由于L2质量损失造成的额外AM损失。(4)模拟恒星在Bb事例氦质量转移过程中产生的重剥带型Ib/c超新星的光曲线。这项裁决反映了美国国家科学基金会的法定任务，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Heat from nuclear reactions inside stars creates pressure that prevents the star from collapsing under its own gravity. However, all stars will ultimately run out of nuclear fuel. When this happens, the star collapses under its own weight and the core will form a very dense, compact remnant. Depending on the mass of the star, the remnant will either be a black hole, neutron star or white dwarf. Many stars are formed in binary systems – two stars that are gravitationally bound to each other. If both stars in a binary evolve to form compact objects, the resulting system is known as a “compact object binary”. Compact object binaries that in-spiral and merge have been observed in recent sky surveys as bright transients and detected as sources of gravitational waves. A team from the California Institute of Technology (Caltech) will study the formation pathways of these compact binary systems. Their results will constrain the physical processes affecting the evolution of these systems, which determine their gravitational wave and electromagnetic signatures. The team will work on a variety of projects designed to retain under-represented minority (URM) undergraduates in STEM fields. In particular, the Principal Investigator (PI) will mentor URM undergraduate and graduate students from Caltech and neighboring institutions. The PI will also participate in Caltech's new FUTURE Ignited program designed to help students of color to prepare for graduate school, including help with the application process and research opportunities at Caltech. Finally, the PI will participate in several public outreach events. The team will use advanced computational techniques to model the formation pathways of binary compact objects. They will focus on understanding how orbital angular momentum (AM) is lost to enable the two remnants to in-spiral and merge. In particular, they will: (1) Perform evolutionary calculations for binary White Dwarf (WD) models with a range of WD masses, initial orbital periods, and hydrogen shell masses to determine the post common envelope conditions of observed WD binaries. (2) Implement extra AM loss via the Lagrangian-2 (L2) point into binary stellar evolution models for a range of progenitor mass, companion mass, and initial orbital period to account for the fact that material can escape through the higher Lagrangian points if the mass transfer rate is high enough. (3) Run binary models that include helium (Case BB) transfer, including extra AM loss due to L2 mass loss. (4) Model the light curves of heavily stripped type Ib/c supernovae produced by stars undergoing Case BB helium mass transfer.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.