HD 191939 exoplanet system radial velocities

Planet b is a sub-Neptune with radius 3.4+/-0.8R_{Earth}_ and mass 10.0+/-0.7M_{Earth}_ with an RM amplitude <1m/s. We find the planet is consistent with a well-aligned orbit, measuring {lambda}=3.7+/-5.0{deg}.

Additionally, we place new constraints on the mass and period of the distant super-Jupiter, planet f, finding it to be 2.88+/-0.26M_J_ on a 2898+/-152days orbit. With these new orbital parameters, we perform a dynamical analysis of the system and constrain the mutual inclination of the nontransiting planet e to be smaller than 12{deg} relative to the plane shared by the inner three transiting planets. Additionally, the further planet f is inclined off this shared plane, the greater the amplitude of precession for the entire inner system, making it increasingly unlikely to measure an aligned orbit for planet b.