KOI-1299: a red giant interacting with one of its two long period giant planets
Quinn et al
We report the discovery of KOI-1299b, a giant planet (Mb=5.41+0.32−0.18MJup,Rb=1.145+0.036−0.039RJup) transiting an evolved star (M⋆=1.32+0.10−0.07M⊙,R⋆=4.06+0.12−0.08R⊙) with an orbital period of Pb=52.501134+0.000070−0.000107 days. Radial velocities (RVs) reveal that KOI-1299b orbits its parent star with an eccentricity of e=0.5134+0.0098−0.0089, which we also measure independently with asterodensity profiling (e=0.507+0.039−0.114), thereby confirming the validity of asterodensity profiling on this particular evolved star. The well determined planetary properties and unusually large mass also make this planet an important benchmark for theoretical models of super-Jupiter formation. Long-term RV monitoring detected the presence of a non-transiting outer planet (KOI-1299c; Mcsinic=2.43+0.22−0.24MJup,Pc=406.2+3.9−2.5 days), and adaptive optics imaging revealed a nearby (0.87"), faint companion (KOI-1299B) that is a physically bound M dwarf. The host star exhibits high S/N asteroseismic oscillations, which enable precise measurements of the stellar mass, radius and age. Analysis of the rotational splitting of the oscillation modes additionally reveals the stellar spin axis to be nearly edge-on, which suggests that the stellar spin is likely well-aligned with the orbit of the transiting planet. Despite its long period, the obliquity of the 52.5-day orbit may have been shaped by star-planet interaction (SPI) in a manner similar to hot Jupiter systems, and we present observational and theoretical evidence to support this scenario. Finally, as a short-period outlier among giant planets orbiting giant stars, study of KOI-1299b may help explain the distribution of massive planets orbiting giant stars interior to 1 AU.