Evidence for Low-level Dynamical Excitation in Near-resonant Exoplanet Systems*

Abstract

The geometries of near-resonant planetary systems offer a relatively pristine window into the initial conditions of exoplanet systems. Given that near-resonant systems have likely experienced minimal dynamical disruptions, the spin–orbit orientations of these systems inform the typical outcomes of quiescent planet formation, as well as the primordial stellar obliquity distribution. However, few measurements have been made to constrain the spin–orbit orientations of near-resonant systems. We present a Rossiter–McLaughlin measurement of the near-resonant warm Jupiter TOI-2202 b, obtained using the Carnegie Planet Finder Spectrograph on the 6.5 m Magellan Clay Telescope. This is the eighth result from the Stellar Obliquities in Long-period Exoplanet Systems survey. We derive a sky-projected 2D spin–orbit angle λ = 26 − 15 + 12 ° and a 3D spin–orbit angle ψ = 31 − 11 + 13 ° , finding that TOI-2202 b—the most massive near-resonant exoplanet with a 3D spin–orbit constraint to date—likely deviates from exact alignment with the host star’s equator. Incorporating the full census of spin–orbit measurements for near-resonant systems, we demonstrate that the current set of near-resonant systems with period ratios P 2/P 1 ≲ 4 is generally consistent with a quiescent formation pathway, with some room for low-level (≲20°) protoplanetary disk misalignments or post-disk-dispersal spin–orbit excitation. Our result constitutes the first population-wide analysis of spin–orbit geometries for near-resonant planetary systems.

The PFS View of TOI-677 b: A Spin–Orbit Aligned Warm Jupiter in a Dynamically Hot System*

“…Recently, Sedaghati et al (2023) We present a new, independent RM measurement across one transit of TOI-677 b with the Carnegie Planet Finder Spectrograph (PFS; Crane et al 2006Crane et al , 2008Crane et al , 2010 on the 6.5 m Magellan Clay telescope. This observation was obtained as part of the Stellar Obliquities in Long-period Exoplanet Systems survey (Rice et al 2021Wang et al 2022;Rice et al 2023aRice et al , 2023bHixenbaugh et al 2023;Lubin et al 2023;Wright et al 2023), and it represents the tenth published result from this program.…”

“…However, the true distribution of spin-orbit angles for each population remains elusive due to a combination of small number statistics and often large uncertainties for individual measurements. Even those systems that are thought to form quiescently and would generally be classified as "aligned" demonstrate some spread in their measured spin-orbit angles (Rice et al 2023b).…”