Brief But Spectacular: New Windows into the Physics of Common Envelope Evolution

各种奇异的致密天体只能由两颗开始于接近双星轨道的恒星合并而成。在一个非常短暂的“共同包络阶段”(CE)中，质量最大的那颗恒星会膨胀并吞没它的伴星，从而产生摩擦，从而缩短两颗恒星之间的距离。对后CE系统的观察非常少，因此该团队将进行大规模的系统搜索，以发现后CE系统。有了这些结果，这一领域的研究人员将能够将他们的计算机模拟与经历了CE阶段的系统的实际轨道和物理性质相匹配。Pi Nordhaus精通美国手语，罗切斯特理工学院国家聋人技术研究所的学生将被招募到该团队进行夏季研究体验。该团队将利用新获得的广泛领域和时间域调查，如Gaia、Tess和ZTF，将使用一种新方法来观察性地确定共同包络进化的初始条件和最终条件之间的映射。在下列条件下，星系团中的成员资格对前CE主星的质量产生了严格的约束：(I)星系团的年龄是已知的，(Ii)白矮星是一个确认的星系团成员，(III.)白矮星的冷却年龄确定得很好，而且比星团年龄短，(iv.)星团关闭质量大于1.5个太阳质量。在这些条件下，系统最有可能作为渐近巨星(AGB)进入公共包络阶段。团簇还有一个额外的好处，那就是金属丰度和关闭质量是已知的，从而进一步减少了建模的不确定性。识别和描述位于星团中的分离的后CE双星的一组基准可能对理论的发展和建立对外来物体产生率的可靠预测具有变革性。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。

A variety of exotic compact objects can be formed only by the merger of two stars that start out in a close binary orbit. During a very short lived “common envelope phase” (CE), the star with the most mass swells and engulfs its companion, resulting in friction that reduces the distance between the stars. Very few observations of post-CE systems exist, so this team will conduct a large-scale systematic search to discover post-CE systems. With these results, researchers in this field will be able to match their computer simulations to the actual orbital and physical properties of systems that have undergone this CE phase. PI Nordhaus is fluent in American Sign Language and students from the Rochester Institute of Technology's National Technical Institute for the Deaf will be recruited for a summer research experience with the team.Leveraging newly available wide-field and time-domain surveys such as Gaia, TESS, and ZTF, the team will use a novel method to observationally determine the mapping between the initial and final conditions of common envelope evolution. Membership in a cluster yields a tight constraint on the pre-CE primary star’s mass under the following conditions: (i.) the cluster’s age is known, (ii.) the white dwarf is a confirmed cluster member, (iii.) the white dwarf cooling age is well determined and shorter than the cluster age, and (iv.) the cluster turn-off mass is above 1.5 solar masses. Under these conditions, the system is most likely to have entered the common envelope phase as an Asymptotic Giant Branch (AGB) star. Clusters have the additional benefit that the metallicity and turn-off masses are known thereby further reducing modeling uncertainty. Identifying and characterizing a set of benchmarks for detached post-CE binaries located in stellar clusters could be transformative to the development of theory and to establishing reliable predictions for production rates of exotic objects.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.