TESS Hunt for Young and Maturing Exoplanets (THYME) XIV: A Comoving-Based Age Constraint for KELT-20

TL;DR

This paper determines the age of the star KELT-20 at approximately 58 million years using a combination of kinematic and stellar activity data, providing insights into early hot Jupiter evolution.

Contribution

It introduces a comprehensive age-dating method for KELT-20 by combining Gaia data, isochronal, gyrochronology, and activity indicators, refining the system's age estimate.

Findings

KELT-20 is approximately 58 million years old.

77 stars share proper motions with KELT-20, confirming group membership.

The age constraint informs models of hot Jupiter formation and migration.

Abstract

Young stellar moving groups offer unique opportunities to investigate the early evolution of stellar and planetary systems. In continuation of an ongoing effort to age-date compelling planetary systems, we provide an in-depth age analysis of KELT-20, a young A-type star that hosts a well-aligned ultra-hot Jupiter. This system poses a useful case study to investigate migration mechanisms at early stages of evolution. Using Gaia DR3 data, we identify 77 stars with proper motions consistent with KELT-20, including 19 with measured radial velocities that enable full 3D kinematic confirmation. Using isochronal analyses, gyrochronology, photometric variability, and stellar activity indicators, we converge on an age of $58 \pm 5\,$Myr. This constraint provides critical insights into the dynamical processes shaping hot Jupiter formation.