Migration origin of TOI-6038 A b

Determine whether high-eccentricity tidal migration driven by an additional, still-undetected companion or early disk-driven migration transported the sub-Saturn TOI-6038 A b (mass 78.5 M⊕, radius 6.41 R⊕) into its present-day close-in circular orbit with period 5.8267311 days around the F-type star TOI-6038 A.

Background

The authors discover TOI-6038 A b, a dense sub-Saturn at the outer edge of the Neptunian ridge, orbiting a bright late F-type star in a wide binary system with TOI-6038 B at ~3217 AU. First-order estimates suggest secular perturbations from TOI-6038 B may be insufficient to drive high-eccentricity tidal migration (HEM), leaving the planet’s close-in orbit unexplained by the known companion.

Given the planet’s location in a regime where HEM is suspected to play a role, clarifying whether HEM (triggered by an undetected companion) or early disk-driven migration set the current orbital architecture is key to understanding TOI-6038 A b’s dynamical history and, more broadly, the processes shaping dense sub-Saturns in the Neptunian ridge.