Common Envelope Evolution and the Origins of Massive Compact Binaries

近双星系统经历了一段短暂的时间，在这段时间里，两颗恒星都嵌入了一个共同的气体包层--公共包络(CE)阶段。在它被抛出之前，包层内的阻力缩小了恒星之间的距离，留下了一个更紧密的系统。如果这两颗恒星都是大质量的(8-100个太阳质量)，可能会产生由中子星和黑洞组成的奇异双星系统，这是人们非常感兴趣的，因为它们可能是伽马射线暴、千诺瓦和重力波源的前身。然而，目前对CE阶段的模拟无法实现许多本应发生的系统的包层抛射，此外还存在轨道收缩不足或“令人振奋”的问题。这种差异被归因于模拟中缺少物理或空间分辨率/持续时间不足。首席研究人员(PI)和团队将使用3D辐射-流体动力学模拟来解决关于大质量、近距离双星系统中CE演化的几个重要问题，方法是首次考虑包层中H/He复合释放的能量以及恒星风和脉动。要解决的问题包括(1)这些机制在包络抛射中可能发挥的作用，(2)什么样的系统结果，以及(3)是否存在允许识别这些事件的观测特征。该奖项还将支持每年一名研究生和两名本科生的研究工作，这是伊利诺伊州天体物理动力学演示网站的扩展，还将参加一个夏季天文夏令营。PI的团队将使用辐射流体动力学模拟来研究由红超巨星和中子星或黑洞同伴组成的公共包层(CE)双星的演化。这种构型在大质量X射线双星、双星黑洞和双星中子星的形成场景中起着关键作用。为了在这些系统中实现包络抛射和激励，他们将使用自适应网格细化模拟，其中包括自洽方式的H和He部分电离和辐射扩散。通过包含依赖于时间的包层加热，研究人员还将探索动力脉动在辅助包层抛射中的作用。通过直接监测出现的辐射通量，它们还将产生光曲线，以确定哪些观测特征可能有助于触发后续的时间域探测观测。这些模拟的结果将直接指导双星种群合成社区的工作，该社区对引力波源、双简并Ia型超新星和X射线双星的数量的预测对这一演化阶段很敏感。这一奖项反映了NSF的法定使命，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。

Close binary systems experience a brief period in which both stars become embedded in a common gaseous envelope - the Common Envelope (CE) phase. Before its ejection, drag forces within the envelope shrink the stars' separation, leaving behind a much closer system. If both stars are massive (8-100 solar masses), exotic binary systems comprised of neutron stars and black holes may result, which are of great interest as being the likely progenitors of gamma-ray bursts, kilonovae, and gravity wave sources. However, current simulations of the CE phase are unable to achieve envelope ejection for many systems in which it should occur, with the added problem of insufficient orbital shrinkage or "inspiraling." This discrepancy has been attributed to missing physics or insufficient spatial resolution/duration in the simulations. The principal investigator (PI) and team will use 3D radiation-hydrodynamical simulations to address several important questions regarding CE evolution in massive, close binary star systems by considering for the first time the energy released by H/He recombination in the envelope as well as stellar winds and pulsations. The questions to be addressed include (1) the possible roles these mechanisms play in envelope ejection, (2) what kinds of systems result, and (3) whether there are observational signatures that will allow these events to be recognized. This award will also support research efforts of one graduate and two undergraduate students each year, an extension of the Illinois Astrophysical Dynamics Demos site, plus participation in a summer astronomy camp.The PI's team will use radiation-hydrodynamic simulations to study the evolution of common envelope (CE) binaries comprised of a red supergiant and a neutron star or black hole companion. This configuration plays a key role in formation scenarios for high-mass X-ray binaries, binary black holes, and binary neutron stars. To achieve envelope ejection and inspiraling in these systems they will use adaptive mesh refinement simulations that include both H and He partial ionization and radiation diffusion in a self-consistent manner. By including time-dependent envelope heating, the researchers will also explore the role of dynamical pulsations in assisting envelope ejection. And by directly monitoring the emergent radiative flux they will also generate light curves to determine which observational signatures might be useful as triggers for follow-up time-domain survey observations. The results of these simulations will directly guide the work of the binary population synthesis community, whose predictions for the number of gravitational wave sources, double degenerate Type Ia supernovae, and X-ray binaries are sensitive to this evolutionary phase.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.