Asteroseismic inference on the spin-orbit misalignment and stellar parameters of HAT-P-7

The measurement of obliquities - the angle between the orbital and stellar rotation - in star-planet systems is of great importance for understanding planet system formation and evolution. The bright and well-studied HAT-P-7 (Kepler-2) system is intriguing because several Rossiter-McLaughlin (RM) measurements found a high projected obliquity in this system, but it was not possible so far to determine whether the orbit is polar and/or retrograde. The goal of this study is to measure the stellar inclination and hereby the full 3D obliquity of the HAT-P-7 system instead of only the 2D projection as measured by the RM effect. In addition, we provide an updated set of stellar parameters for the star. The new parameters for the star give an updated planetary density of [rho][subp]= 0.65 + or - 0.03 g cm[sup -3], which is lower than previous estimates.