Common Envelope Evolution and the Origins of Massive Compact Binaries

近距离双星系统会经历一个短暂的时期，在这段时期内，两颗恒星都被嵌入到一个共同的气体包层中--共同包层（CE）阶段。在它被抛出之前，包层内的拖曳力缩小了恒星的距离，留下了一个更近的系统。如果两颗恒星都是大质量的（8-100太阳质量），那么可能会产生由中子星和黑洞组成的奇异双星系统，这是非常有趣的，因为它们可能是伽马射线暴，千新星和重力波源的祖先。然而，目前对CE阶段的模拟无法实现许多系统的包线弹射，而在这些系统中，它应该发生，并增加了轨道收缩不足或“吸气”的问题。“这种差异归因于模拟中缺少物理或空间分辨率/持续时间不足。首席研究员（PI）和团队将使用3D辐射流体动力学模拟来解决几个重要的问题，通过考虑第一次在信封中的H/He复合以及恒星风和脉动释放的能量，在大规模的近距离双星星星系统CE演变。要解决的问题包括：（1）这些机制在包络弹射中可能扮演的角色;（2）产生什么样的系统;（3）是否存在观测信号，允许识别这些事件。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，伊利诺伊天体物理动力学演示网站的扩展，以及参加夏季天文学夏令营。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星或黑洞伴星组成的共同包络（CE）双星的演化。这种结构在大质量X射线双星、双黑洞和双中子星的形成过程中起着关键作用。为了在这些系统中实现包络喷射和吸气，他们将使用自适应网格细化模拟，其中包括H和He部分电离和辐射扩散以自洽的方式。通过包括随时间变化的包络加热，研究人员还将探索动态脉动在辅助包络喷射中的作用。通过直接监测出射辐射通量，他们还将生成光变曲线，以确定哪些观测特征可能有助于触发后续的时域调查观测。这些模拟的结果将直接指导双星总体合成社区的工作，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。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值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.