The obliquity of HIP 67522 b: a 17 Myr old transiting hot Jupiter-sized planet

Abstract

HIP 67522 b is a 17 Myr old, close-in ($P_{orb}=6.96$ d), Jupiter-sized ($R=10R_{\oplus }$) transiting planet orbiting a Sun like star in the Sco-Cen OB association. We present our measurement of the system's projected orbital obliquity via two spectroscopic transit observations using the CHIRON spectroscopic facility. We present a global model that accounts for large surface brightness features typical of such young stars during spectroscopic transit observations. With a value of $|\hat{I}»|=5.8_{-5.7}^{+2.8\circ }$, it is unlikely that this well-aligned system is the result of a high eccentricity driven migration history. By being the youngest planet with a known obliquity, HIP 67522 b holds a special place in contributing to our understanding of giant planet formation and evolution. Our analysis shows the feasibility of such measurements for young and very active stars.

10 pages, 3 figures, 1 table. Accepted for publication in the Astrophysical Journal Letters (10/27/2021)