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

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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.