Astroseminar - Steffani Grondin

Steffani Grondin is a final-year PhD candidate in the Department of Astronomy and Astrophysics at the University of Toronto. Her research focuses on the evolution of compact object binaries and the common envelope phase, using star clusters as laboratories to study binary evolution. Steffani is also the main developer of Corespray, a Python package that efficiently simulates dynamical interactions in star clusters. Her software has provided new insights into a variety of Milky Way science cases, including hypervelocity stars, stellar streams and the composition of the Galactic halo.

Title: Unraveling Common Envelope Evolution: A New Window from Star Clusters

Abstract: Close compact object binaries are the precursors to Type Ia supernovae and gravitational wave events. While most short-period binaries are believed to have evolved through at least one common envelope (CE) phase, our understanding of CE evolution remains one of the largest unresolved issues in stellar astrophysics, mainly due to the lack of observational benchmarks that connect post-CE parameters with their pre-CE initial conditions. Identifying post-CE systems in star clusters can circumvent this issue by providing an independent constraint on the system’s age, but until recently, there were only two white dwarf-main sequence (WD+MS) post-CE systems associated with a star cluster. In this talk, I will describe our discovery of the first population of candidate WD+MS binaries in Milky Way star clusters. First, I will discuss our new catalog of 52 WD+MS candidate binaries in 38 open star clusters identified through multi-wavelength observations and supervised machine learning. Next, I will detail the ongoing follow-up characterization of a subset of systems that has led to the confirmation of new WD+MS post-CE systems in clusters. Finally, I will outline how we can expand this sample by using novel star cluster simulations to link field binaries with their birth clusters. These efforts will ultimately provide fundamental observational constraints on one of the most uncertain yet crucial phases of binary evolution.