A Manim-style talk about my Honours work on common envelope.
The common envelope governs the formation of a diverse range of astrophysical phenomena, from Type Ia SNe to mergers of stellar-mass black holes. Yet, this interaction is one of the most poorly understood phases of binary evolution. Current models rely heavily on the traditional energy balance (α) formalism, which has consistently failed to reproduce observed post-common envelope populations with its simple physical assumptions.
The two-stage formalism introduced by Hirai & Mandel (2022) offers a more physically motivated approach by separately modelling the inspiral and envelope ejection. However, this framework has only been studied for high-mass stars (>12 M☉). Intermediate-mass stars (2–8 M☉) share a similar structure on the red giant branch to their high-mass counterparts, suggesting the formalism is also relevant. These stars produce the massive white dwarfs that serve as the progenitors for Type Ia supernovae and accretors in novae systems.
Here, I present the first systematic application of the two-stage formalism to intermediate-mass stars with binary population synthesis. I compare predicted post-common envelope orbital separations and binary properties against both the traditional α-formalism and observations of post-common envelope binaries. These results provide crucial tests of common envelope physics, and offer us new insights into the formation pathways for the progenitors of these diverse phenomena.