A Tendency Toward Alignment in Single-Star Warm Jupiter Systems

Malena Rice, Songhu Wang, Xian-Yu Wang, Gudmundur Stefansson, Howard Isaacson, Andrew W. Howard, Sarah E. Logsdon, Heidi Schweiker, Fei Dai, Casey Brinkman, Steven Giacalone, Rae Holcomb

Submitted on 13 July 2022


The distribution of spin-orbit angles for systems with wide-separation, tidally detached exoplanets offers a unique constraint on the prevalence of dynamically violent planetary evolution histories. Tidally detached planets provide a relatively unbiased view of the primordial stellar obliquity distribution, since they cannot tidally realign within the system lifetime. We present the third result from our Stellar Obliquities in Long-period Exoplanet Systems (SOLES) survey: a measurement of the Rossiter-McLaughlin effect across two transits of the tidally detached warm Jupiter TOI-1478 b with the WIYN/NEID and Keck/HIRES spectrographs, revealing a sky-projected spin-orbit angle λ=6.25.5+5.9 degrees. Combining this new measurement with the full set of archival obliquity measurements, including two previous constraints from the SOLES survey, we demonstrate that, in single-star systems, tidally detached warm Jupiters are preferentially more aligned than closer-orbiting hot Jupiters. This finding has two key implications: (1) planets in single-star systems tend to form within aligned protoplanetary disks, and (2) warm Jupiters form more quiescently than hot Jupiters, which, in single-star systems, are likely perturbed into a misaligned state through planet-planet interactions in the post-disk-dispersal phase. We also find that lower-mass Saturns span a wide range of spin-orbit angles, suggesting a prevalence of planet-planet scattering and/or secular mechanisms in these systems.


Comment: Accepted for publication in AJ. 20 pages, 7 figures, 4 tables

Subjects: Astrophysics - Earth and Planetary Astrophysics; Astrophysics - Solar and Stellar Astrophysics