Nodal Precession and Tidal Evolution of Two Hot Jupiters: WASP-33 b and KELT-9 b

Abstract

Hot Jupiters orbiting rapidly rotating stars on inclined orbits undergo tidally induced nodal precession measurable over several years of observations. The Hot Jupiters WASP-33 b and KELT-9 b are particularly interesting targets because they are among the hottest planets found to date, orbiting relatively massive stars. Here, we analyze archival and new data that span 11 and 5 yr for WASP-33 b and KELT-9 b, respectively, in order to model and improve upon their tidal precession parameters. Our work confirms the nodal precession for WASP-33 b and presents the first clear detection of the precession of KELT-9 b. We determine that WASP-33 and KELT-9 have gravitational quadrupole moments ( 6.3 − 0.8 + 1.2 ) × 10 − 5 and ( 3.26 − 0.80 + 0.93 ) × 10 − 4 , respectively. We estimate the planets’ precession periods to be 1460 − 130 + 170 yr and 890 − 140 + 200 yr, respectively, and that they will cease to transit their host stars around the years 2090 − 10 + 17 CE and 2074 − 10 + 12 CE, respectively. Additionally, we investigate both planets’ tidal and orbital evolution, suggesting that a high-eccentricity tidal migration scenario is possible to produce both system architectures and that they will most likely not be engulfed by their hosts before the end of their main-sequence lifetimes.