Quiet Dynamical History of the Youngest Transiting Planetary System

Young exoplanets serve as valuable laboratories for testing planet-formation and evolution scenarios, as they retain primordial information about their orbits and atmospheres. TIDYE-1 (IRAS 04125+2902, TOI-6963; Barber et al. 2024), a ~3 Myr T-Tauri star with an effective temperature of ~4080K, is currently the youngest known system hosting a transiting planet. It hosts a Jupiter-sized planet on an edge-on (inclination ~ 90°) orbit while the transitional disk appears closer to face-on (~ 30°), which suggests a complex dynamical history, such as a warped outer disk or orbital misalignment induced during the system’s evolution.

To understand its dynamical history through constraining its obliquity, we measured the Rossiter-McLaughlin effect: stellar radial velocity anomaly during transit. We obtained two transits of TIDYE-1 b using Subaru/IRD. Our analysis yields a projected obliquity of λ =−20^{+13}_{−18} deg, suggesting a spin-orbit-aligned configuration. Combined with Maroon-X observations (Barber et al. 2025), our results support the scenario that the disk is the one misaligned relative to the inner system (Barber et al. 2024).

We also conducted multi-epoch transit monitoring to search for transit timing variations (TTVs), using the MuSCAT series and Sinistro instruments at telescopes worldwide. No TTV signals with amplitudes exceeding 10 minutes were detected, suggesting no strong evidence for a companion capable of producing detectable timing variations. Taken together, our results suggest that the planet has likely undergone relatively quiet dynamical evolution, which provides important context for interpreting its atmospheric properties with future observations.