PALS: Brandon Radzom (IU Bloomington), Hot and (Un)Bothered: Unveiling the Complex Dynamical Histories of Hot Jupiters

Hot and (Un)Bothered: Unveiling the Complex Dynamical Histories of Hot Jupiters

Brandon Radzom
Astronomy PhD candidate
Indiana University - Bloomington

Abstract: The origins of hot Jupiters remains one of the longest-standing puzzles in the field of exoplanets. Hot Jupiters’ frequent orbital misalignment with the stellar spin axis is often cited as evidence of violent high-eccentricity tidal migration, despite there being several mechanisms to tilt their primordial disk-phase orientations. Independently, the observed paucity of neighboring planetary companions to hot Jupiters is also regarded as a robust signature of violent migration — but recent discoveries of several hot Jupiters in compact multi-planet systems challenge this picture. The tight, dynamically pristine configurations of such systems, however, allow them to act as reliable tracers of the disk plane, enabling the study of their primordial obliquity distribution. Combining new Rossiter-McLaughlin measurements with the literature, I find that such compact systems are well-aligned and thus likely formed well-aligned, indicating that misalignment is gained through post-disk interactions. Further, I leverage population-level trends to show that misalignment is restricted to giants with short tidal circularization timescales, providing strong support for high-eccentricity migration specifically. Motivated by their newly-found neighbors, I also run N-body simulations of short-period giants in compact configurations to study the companionship outcomes of quiescent formation. I find that hot Jupiters naturally generate larger companion separations and mutual inclinations compared to longer-period giants, demonstrating that their observed isolation is not unique to violent migration. This provides important context for observations and suggests that quiescent origins may play a larger role than previously thought.

Host:  Hayley Beltz