ES-03-0004

New Obliquity Constraints on a Planetary-Mass Companion

Michael Poon, Marta Bryan, Hanno Rein, Brendan Bowler

Planet obliquities, the orientation between the planet spin axis and orbital plane, can tell us about formation histories. Our solar system has a wide range of obliquities. Earth’s obliquity is 23 degrees, which gives us seasons, secular spin-orbit resonances could explain why Saturn is tilted, and collisions could be the reason why Uranus spins on its side. Up until 2020, obliquities were only known for planets in our Solar System. Currently, there are three exoplanet obliquity measurements. We present preliminary constraints on the fourth. Using near-IR high-resolution spectra from Gemini/IGRINS, we measure a projected rotational velocity (vsini) and radial velocity. The projected rotational velocity, together with a rotation period constrains the planet spin axis inclination, and the relative orientation of this spin axis with the orbit normal gives us the obliquity. We use this obliquity to evaluate possible formation and evolutionary scenarios.