Planetary Masses En Masse (And Down To 1 Earth Mass)

Measuring the mass of planets is of extreme importance, but is challenging particularly in the low mass range. Here we use PyDynamicaLC (Yoffe et al. 2021) to continue our effort to model the smallest — and lowest TTV (transit timing variations) amplitude — of the Kepler planets by using the least-number and least-correlated degrees of freedom needed to produce a photodynamical model. We analyse 45 systems containing 155 planets, for 81 of which we were able to determine significant masses (to better than 3σ). Of the planets with determined masses, 19 are new mass determination with no previous significant literature value, nearly all of them are now measured to have masses lower than 10M_Earth, and down to one Earth mass. For the 62 planets that already had literature mass estimations, we were able to reduce the relative mass error by ~20% (median value).

These results demonstrate the power of using a reduced dimensionality photodynamical model, as ever lower-amplitude TTVs of small planets are detected. The approach is increasingly useful as the TESS mission gathers progressively longer-baseline light curves and for the analysis of the future PLATO mission data, among others.