Collaborative Research: One Step Back and Two Steps Forward: Understanding Gravitational Wave Progenitors by Leveraging Binary Stars in the Local Universe

About This Grant

Although gravitational wave (GW) instruments have been detecting the mergers of two compact objects (either black holes or neutron stars) for nearly a decade, there is still uncertainty about how these binary systems form and develop over time. A research collaboration between Carnegie Mellon University (CMU) and the University of Arizona (UA) will investigate the formation of merging double compact objects by combining state-of-the-art population synthesis tools, used to model large populations of stellar objects, with detailed modelling of binary system development. The project will also support science teacher training programs at both universities: the Physics Teacher Program to connect high school physics teachers with CMU researchers, and the UA University Borderlands Education Center to create workshops that empower high school teachers to use research products in their classrooms. The use of binary population synthesis and detailed binary development modeling has been widely applied to understanding how isolated binary star populations can produce merging double compact objects. However, the assumptions usually made in population synthesis are unable to resolve the effects of the interior structural development of each stellar component in a given binary. This project will unite these previously disparate efforts through a new technique, BackPop, which simulates joint posterior distributions for uncertain binary interaction parameters that reproduce the observed properties of individual binary systems. These joint distributions can then be used to initialize detailed binary development models, which capture the effects of binary mass exchange on the interior structure of each star, thus testing the interaction parameters. The research will focus on three key populations: the binary black holes that make up the global merger rate maximum, the asymmetric mass ratio mergers that are treated as outliers in GW population analysis, and finally, the remaining population consisting of more massive black holes. 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.