The evolutionary history of an extrasolar system is, in part, fossilized through its planets' orbital orientations relative to the host star's spin axis. However, spin-orbit constraints for warm Jupiters -- particularly in binary star systems, which are amenable to a wide range of dynamical processes -- are relatively scarce. We report a measurement of the Rossiter-McLaughlin effect, observed with the Keck/HIRES spectrograph, across the transit of Qatar-6 A b: a warm Jupiter orbiting one star within a binary system. From this measurement, we obtain a sky-projected spin-orbit angle λ=0.1±2.6∘. Combining this new constraint with the stellar rotational velocity of Qatar-6 A that we measure from TESS photometry, we derive a true obliquity ψ=21.82−18.36+8.86∘ -- consistent with near-exact alignment. We also leverage astrometric data from Gaia DR3 to show that the Qatar-6 binary star system is edge-on (iB=90.17−1.06+1.07∘), such that the stellar binary and the transiting exoplanet orbit exhibit line-of-sight orbit-orbit alignment. Ultimately, we demonstrate that all current constraints for the 3-body Qatar-6 system are consistent with both spin-orbit and orbit-orbit alignment. High-precision measurements of the projected stellar spin rate of the host star and the sky-plane geometry of the transit relative to the binary plane are required to conclusively verify the full 3D configuration of the system.
@article{arxiv.2212.02542,
title = {The Orbital Architecture of Qatar-6: A Fully Aligned 3-Body System?},
author = {Malena Rice and Songhu Wang and Konstantin Gerbig and Xian-Yu Wang and Fei Dai and Dakotah Tyler and Howard Isaacson and Andrew W. Howard},
journal= {arXiv preprint arXiv:2212.02542},
year = {2023}
}