Stellar Interactions: Accretion, Migration and Explosions

Multi-star systems are abundant and their evolution can lead to diverse, sometimes exotic, outcomes. These systems experience episodic mass transfer and common envelope evolution (CEE), which can significantly alter orbital dynamics through interactions with gaseous envelopes. While CEE is well-known in compact binaries, it also plays a key role in hierarchical triple systems.

In this talk, I will present 3D hydrodynamical simulations of CEE, including triple-common envelope evolution. I will consider two scenarios based on the distant third star—one in which the third star is the donor (circumstellar case) and one in which it is the accretor (circumbinary case). These interactions can result in stellar mergers, unique compact binary systems, explosive transients, and gravitational wave sources.

I will also discuss how these simulations reveal changes in orbital eccentricity during inspiral, providing constraints on the CEE process. Finally, I will examine explosive outcomes from remnant white dwarf mergers or collisions and how to identify configurations that might trigger a detonation.