TAPIR Seminar

In person: 370 Cahill. To Join via Zoom: 851 0756 7442

Abstract: White dwarf (WD) stars are the final evolutionary stage of most stars in the Galaxy. During WD cooling, the dense, strongly coupled plasma in their interiors can form a solid lattice from the core outward. Such a phase transition not only releases latent heat, which delays cooling, but also induces a compositional buoyancy instability in the remaining liquid (coupled plasma). This instability drives convection that mixes the material and can potentially power a dynamo, generating a magnetic field. Recent observations show that highly magnetized WDs appear preferentially at late cooling ages, when a significant portion of the WD interior is predicted to be crystallized. In this talk, I present results that combine mixing-length theory, WD evolutionary models, and hydrodynamical simulations to investigate crystallization-driven convection in WD interiors in detail. These results are used to estimate the strength of the magnetic field and its evolution as it reaches the surface of the WD. We compare the model predictions with observations and evaluate the feasibility of the crystallization-driven dynamo. Additionally, toward the end of the talk, I discuss some improvements we propose in current cooling models that include crystallization, as well as alternative scenarios that may explain magnetism in WDs.