The Spin–Orbit Misalignment of TOI-1842b: The First Measurement of the Rossiter–McLaughlin Effect for a Warm Sub-Saturn around a Massive Star

Abstract

The mechanisms responsible for generating spin–orbit misalignments in exoplanetary systems are still not fully understood. It is unclear whether these misalignments are related to the migration of hot Jupiters or are a consequence of general star and planet formation processes. One promising method to address this question is to constrain the distribution of spin–orbit angle measurements for a broader range of planets beyond hot Jupiters. In this work, we present the sky-projected obliquity ( λ = − 68 .° 1 − 14.7 + 21.2 ) for the warm sub-Saturn TOI-1842b, obtained through a measurement of the Rossiter–McLaughlin effect using WIYN/NEID. From this, we determine the resulting 3D obliquity (ψ) to be ψ = 73 .° 3 − 12.9 + 16.3 . As the first spin–orbit angle determination made for a sub-Saturn-mass planet around a massive ( M * = 1.45 M ☉) star, our result presents an opportunity to examine the orbital geometries for new regimes of planetary systems. When combined with archival measurements, our observations of TOI-1842b support the hypothesis that the previously established prevalence of misaligned systems around hot, massive stars may be driven by planet–planet dynamical interactions. In massive stellar systems, multiple gas giants are more likely to form and can then dynamically interact with each other to excite spin–orbit misalignments.

SOLES. VII. The Spin–Orbit Alignment of WASP-106 b, a Warm Jupiter along the Kraft Break

“…These hotter stars are also more likely to host more massive protoplanetary disks (Andrews et al 2013), which may be more likely to form multiple Jupiters capable of inducing misalignment through postdisk dynamical sculpting (Wu et al 2023). In this case, the current spin-orbit distribution would directly reflect the planet formation process, with tides playing a lesser role in altering stellar obliquities over time (Hixenbaugh et al 2023). Accordingly, we would expect that the population of warm Jupiters orbiting hot stars would follow a comparable spin-orbit distribution to that of the hot Jupiters orbiting hot stars.…”

“…3. Hot Jupiters orbiting cool stars form and evolve in a similar, quiescent manner to warm Jupiters, and they are therefore initially aligned (Wu et al 2023;Hixenbaugh et al 2023).…”

“…One way to break this degeneracy is to obtain spin-orbit measurements for wider-orbiting, "tidally detached" systemsthat is, those that have projected tidal realignment timescales longer than the age of the system (Rice et al 2021). This is the goal of the Stellar Obliquities in Long-period Exoplanet Systems (SOLES) survey (Rice et al 2021;Wang et al 2022;Rice et al 2022bRice et al , 2023Hixenbaugh et al 2023;Dong et al 2023), which is collecting stellar obliquity measurements for systems with tidally detached planets to more robustly constrain the origins of spin-orbit misalignments in exoplanet systems. By expanding the set of spin-orbit constraints for tidally detached warm Jupiters-which we define as shortperiod (P < 100 days) giant planets (M p 0.4M J ) with scaled orbital semimajor axes a/R * 11-we can place new constraints on the origins of spin-orbit misalignments more generally.…”

TOI-1670 c, a 40 day Orbital Period Warm Jupiter in a Compact System, Is Well Aligned

“…measurements via the Rossiter-McLaughlin (RM) effect. In this work, which expands upon prior investigations of warm Jupiter obliquities (Rice et al 2021(Rice et al , 2022(Rice et al , 2023Wang et al 2022;Dong et al 2023;Hixenbaugh et al 2023;Wright et al 2023), we investigate a system that contains two confirmed transiting exoplanets, one of which is a warm Jupiter. TOI-1670 is a bright (V = 9.9) F7V star (Pecaut & Mamajek 2013) that hosts a transiting 11 days orbital period sub-Neptune (b) and a transiting 40 day orbital period Jovian (c) (Tran et al 2022).…”

The Orbit of Warm Jupiter WASP-106 b is Aligned with its Star

“…Lately, there have been numerous measurements of the true 3D obliquities that require the stellar inclination to be measured in addition to the projected obliquity; see, e.g., Cegla et al (2016), Bourrier et al (2023), and Doyle et al (2023. Depending on the orientation of the stellar spin axis with regard to our line of sight to the observed system, the projected and 3D obliquity can be quite different from one another (see e.g., Hixenbaugh et al 2023).…”